refactor(cli/tests): remove unnecessary void return types (#11577)

121 files changed, 1095 insertions, 1177 deletions

diff --git a/cli/tests/004_set_timeout.ts b/cli/tests/004_set_timeout.ts
index 58f899ee3..214b25086 100644
--- a/cli/tests/004_set_timeout.ts
+++ b/cli/tests/004_set_timeout.ts
@@ -1,10 +1,10 @@
-setTimeout((): void => {
+setTimeout(() => {
   console.log("World");
 }, 10);
 
 console.log("Hello");
 
-const id = setTimeout((): void => {
+const id = setTimeout(() => {
   console.log("Not printed");
 }, 10000);
 
diff --git a/cli/tests/012_async.ts b/cli/tests/012_async.ts
index 773272ca1..536197b68 100644
--- a/cli/tests/012_async.ts
+++ b/cli/tests/012_async.ts
@@ -1,6 +1,6 @@
 // Check that we can use the async keyword.
-async function main(): Promise<void> {
-  await new Promise((resolve): void => {
+async function main() {
+  await new Promise((resolve) => {
     console.log("2");
     setTimeout(resolve, 100);
   });
diff --git a/cli/tests/013_dynamic_import.ts b/cli/tests/013_dynamic_import.ts
index 6bbce3132..d4dc55152 100644
--- a/cli/tests/013_dynamic_import.ts
+++ b/cli/tests/013_dynamic_import.ts
@@ -1,4 +1,4 @@
-(async (): Promise<void> => {
+(async () => {
   const { returnsHi, returnsFoo2, printHello3 } = await import(
     "./subdir/mod1.ts"
   );
diff --git a/cli/tests/014_duplicate_import.ts b/cli/tests/014_duplicate_import.ts
index 97864fea7..88f934526 100644
--- a/cli/tests/014_duplicate_import.ts
+++ b/cli/tests/014_duplicate_import.ts
@@ -4,6 +4,6 @@ import "./subdir/auto_print_hello.ts";
 
 import "./subdir/auto_print_hello.ts";
 
-(async (): Promise<void> => {
+(async () => {
   await import("./subdir/auto_print_hello.ts");
 })();
diff --git a/cli/tests/016_double_await.ts b/cli/tests/016_double_await.ts
index 0f31b3a80..457a53ff3 100644
--- a/cli/tests/016_double_await.ts
+++ b/cli/tests/016_double_await.ts
@@ -1,6 +1,6 @@
 // This is to test if Deno would die at 2nd await
 // See https://github.com/denoland/deno/issues/919
-(async (): Promise<void> => {
+(async () => {
   const currDirInfo = await Deno.stat(".");
   const parentDirInfo = await Deno.stat("..");
   console.log(currDirInfo.isDirectory);
diff --git a/cli/tests/018_async_catch.ts b/cli/tests/018_async_catch.ts
index 85423ceda..ac43a52e8 100644
--- a/cli/tests/018_async_catch.ts
+++ b/cli/tests/018_async_catch.ts
@@ -1,7 +1,7 @@
 function fn(): Promise<never> {
   throw new Error("message");
 }
-async function call(): Promise<void> {
+async function call() {
   try {
     console.log("before await fn()");
     await fn();
@@ -11,4 +11,4 @@ async function call(): Promise<void> {
   }
   console.log("after try-catch");
 }
-call().catch((): void => console.log("outer catch"));
+call().catch(() => console.log("outer catch"));
diff --git a/cli/tests/025_hrtime.ts b/cli/tests/025_hrtime.ts
index 9f60b7a77..b69d61488 100644
--- a/cli/tests/025_hrtime.ts
+++ b/cli/tests/025_hrtime.ts
@@ -1,4 +1,4 @@
-window.onload = async (): Promise<void> => {
+window.onload = async () => {
   console.log(performance.now() % 2 !== 0);
   await Deno.permissions.revoke({ name: "hrtime" });
   console.log(performance.now() % 2 === 0);
diff --git a/cli/tests/028_args.ts b/cli/tests/028_args.ts
index f3604a830..ec41d52f9 100644
--- a/cli/tests/028_args.ts
+++ b/cli/tests/028_args.ts
@@ -1,3 +1,3 @@
-Deno.args.forEach((arg): void => {
+Deno.args.forEach((arg) => {
   console.log(arg);
 });
diff --git a/cli/tests/034_onload/imported.ts b/cli/tests/034_onload/imported.ts
index 9e1411bea..3c7a0aae2 100644
--- a/cli/tests/034_onload/imported.ts
+++ b/cli/tests/034_onload/imported.ts
@@ -1,7 +1,7 @@
 import { assert } from "../../../test_util/std/testing/asserts.ts";
 import "./nest_imported.ts";
 
-const handler = (e: Event): void => {
+const handler = (e: Event) => {
   assert(!e.cancelable);
   console.log(`got ${e.type} event in event handler (imported)`);
 };
diff --git a/cli/tests/034_onload/main.ts b/cli/tests/034_onload/main.ts
index f8c48ba7b..7696ec122 100644
--- a/cli/tests/034_onload/main.ts
+++ b/cli/tests/034_onload/main.ts
@@ -4,7 +4,7 @@ import "./imported.ts";
 assert(window.hasOwnProperty("onload"));
 assert(window.onload === null);
 
-const eventHandler = (e: Event): void => {
+const eventHandler = (e: Event) => {
   assert(!e.cancelable);
   console.log(`got ${e.type} event in event handler (main)`);
 };
@@ -13,12 +13,12 @@ window.addEventListener("load", eventHandler);
 
 window.addEventListener("unload", eventHandler);
 
-window.onload = (e: Event): void => {
+window.onload = (e: Event) => {
   assert(!e.cancelable);
   console.log(`got ${e.type} event in onload function`);
 };
 
-window.onunload = (e: Event): void => {
+window.onunload = (e: Event) => {
   assert(!e.cancelable);
   console.log(`got ${e.type} event in onunload function`);
 };
diff --git a/cli/tests/034_onload/nest_imported.ts b/cli/tests/034_onload/nest_imported.ts
index d43b8ebe7..8ca668de9 100644
--- a/cli/tests/034_onload/nest_imported.ts
+++ b/cli/tests/034_onload/nest_imported.ts
@@ -1,6 +1,6 @@
 import { assert } from "../../../test_util/std/testing/asserts.ts";
 
-const handler = (e: Event): void => {
+const handler = (e: Event) => {
   assert(!e.cancelable);
   console.log(`got ${e.type} event in event handler (nest_imported)`);
 };
diff --git a/cli/tests/045_proxy_test.ts b/cli/tests/045_proxy_test.ts
index 6e338f4fc..db6f00876 100644
--- a/cli/tests/045_proxy_test.ts
+++ b/cli/tests/045_proxy_test.ts
@@ -4,7 +4,7 @@ import { assertEquals } from "../../test_util/std/testing/asserts.ts";
 
 const addr = Deno.args[1] || "127.0.0.1:4555";
 
-async function proxyServer(): Promise<void> {
+async function proxyServer() {
   const server = serve(addr);
 
   console.log(`Proxy server listening on http://${addr}/`);
@@ -13,7 +13,7 @@ async function proxyServer(): Promise<void> {
   }
 }
 
-async function proxyRequest(req: ServerRequest): Promise<void> {
+async function proxyRequest(req: ServerRequest) {
   console.log(`Proxy request to: ${req.url}`);
   const proxyAuthorization = req.headers.get("proxy-authorization");
   if (proxyAuthorization) {
@@ -31,7 +31,7 @@ async function proxyRequest(req: ServerRequest): Promise<void> {
   });
 }
 
-async function testFetch(): Promise<void> {
+async function testFetch() {
   const c = Deno.run({
     cmd: [
       Deno.execPath(),
@@ -52,7 +52,7 @@ async function testFetch(): Promise<void> {
   c.close();
 }
 
-async function testModuleDownload(): Promise<void> {
+async function testModuleDownload() {
   const http = Deno.run({
     cmd: [
       Deno.execPath(),
@@ -72,7 +72,7 @@ async function testModuleDownload(): Promise<void> {
   http.close();
 }
 
-async function testFetchNoProxy(): Promise<void> {
+async function testFetchNoProxy() {
   const c = Deno.run({
     cmd: [
       Deno.execPath(),
@@ -94,7 +94,7 @@ async function testFetchNoProxy(): Promise<void> {
   c.close();
 }
 
-async function testModuleDownloadNoProxy(): Promise<void> {
+async function testModuleDownloadNoProxy() {
   const http = Deno.run({
     cmd: [
       Deno.execPath(),
@@ -115,7 +115,7 @@ async function testModuleDownloadNoProxy(): Promise<void> {
   http.close();
 }
 
-async function testFetchProgrammaticProxy(): Promise<void> {
+async function testFetchProgrammaticProxy() {
   const c = Deno.run({
     cmd: [
       Deno.execPath(),
diff --git a/cli/tests/055_info_file_json.out b/cli/tests/055_info_file_json.out
index de0091ded..070668922 100644
--- a/cli/tests/055_info_file_json.out
+++ b/cli/tests/055_info_file_json.out
@@ -22,7 +22,7 @@
           "code": "file://[WILDCARD]/cli/tests/subdir/subdir2/mod2.ts"
         }
       ],
-      "size": 320,
+      "size": 308,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]mod1.ts",
       [WILDCARD]
@@ -30,7 +30,7 @@
     {
       "specifier": "file://[WILDCARD]/cli/tests/subdir/print_hello.ts",
       "dependencies": [],
-      "size": 63,
+      "size": 57,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]print_hello.ts",
       [WILDCARD]
@@ -43,11 +43,11 @@
           "code": "file://[WILDCARD]/cli/tests/subdir/print_hello.ts"
         }
       ],
-      "size": 163,
+      "size": 157,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]mod2.ts",
       [WILDCARD]
     }
   ],
-  "size": 757
+  "size": 733
 }
diff --git a/cli/tests/076_info_json_deps_order.out b/cli/tests/076_info_json_deps_order.out
index 55cf05b30..f8b26057d 100644
--- a/cli/tests/076_info_json_deps_order.out
+++ b/cli/tests/076_info_json_deps_order.out
@@ -26,10 +26,10 @@
           "code": "file://[WILDCARD]/cli/tests/recursive_imports/common.ts"
         }
       ],
-      "size": 114,
+      "size": 108,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]A.ts",
-      "checksum": "da204c16d3114763810864083af8891a887d65fbe34e4c8b5bf985dbc8f0b01f"
+      "checksum": "3b45a105d892584298490cb73372b2cac57118e1e42a677a1d5cacea704d8d3a"
     },
     {
       "specifier": "file://[WILDCARD]/cli/tests/recursive_imports/B.ts",
@@ -43,10 +43,10 @@
           "code": "file://[WILDCARD]/cli/tests/recursive_imports/common.ts"
         }
       ],
-      "size": 114,
+      "size": 108,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]B.ts",
-      "checksum": "060ef62435d7e3a3276e8894307b19cf17772210a20dd091d24a670fadec6b83"
+      "checksum": "b12b0437ef9a91c4a4b1f66e8e4339f986b60bd8134031ccb296ce49df15b54e"
     },
     {
       "specifier": "file://[WILDCARD]/cli/tests/recursive_imports/C.ts",
@@ -60,19 +60,19 @@
           "code": "file://[WILDCARD]/cli/tests/recursive_imports/common.ts"
         }
       ],
-      "size": 132,
+      "size": 126,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]C.ts",
-      "checksum": "5190563583617a69f190f1cc76e6552df878df278cfaa5d5e30ebe0938cf5e0b"
+      "checksum": "605875a410741bfaeeade28cbccf45f219ad99d987ea695e35eda75d2c53a658"
     },
     {
       "specifier": "file://[WILDCARD]/cli/tests/recursive_imports/common.ts",
       "dependencies": [],
-      "size": 34,
+      "size": 28,
       "mediaType": "TypeScript",
       "local": "[WILDCARD]common.ts",
-      "checksum": "01b595d69514bfd001ba2cf421feabeaef559513f10697bf1a22781f8a8ed7f0"
+      "checksum": "c70025f0b936c02980c3be1fbd78f6f36b6241927c44ea67580821a6e664d8b3"
     }
   ],
-  "size": 475
+  "size": 451
 }
diff --git a/cli/tests/bundle/file_tests-fixture11.ts b/cli/tests/bundle/file_tests-fixture11.ts
index d3f60d367..1c361438f 100644
--- a/cli/tests/bundle/file_tests-fixture11.ts
+++ b/cli/tests/bundle/file_tests-fixture11.ts
@@ -2,7 +2,7 @@ import { a as defaultA, O } from "./subdir/m.ts";
 export { O } from "./subdir/m.ts";
 
 interface AOptions {
-  a?(): void;
+  a?();
   c?: O;
 }
 
diff --git a/cli/tests/bundle_im.ts b/cli/tests/bundle_im.ts
index c43f6294c..74834de20 100644
--- a/cli/tests/bundle_im.ts
+++ b/cli/tests/bundle_im.ts
@@ -8,10 +8,10 @@ export function returnsFoo2(): string {
   return returnsFoo();
 }
 
-export function printHello3(): void {
+export function printHello3() {
   printHello2();
 }
 
-export function throwsError(): void {
+export function throwsError() {
   throw Error("exception from mod1");
 }
diff --git a/cli/tests/cat.ts b/cli/tests/cat.ts
index 0cfd99d22..14ceec553 100644
--- a/cli/tests/cat.ts
+++ b/cli/tests/cat.ts
@@ -1,5 +1,5 @@
 import { copy } from "../../test_util/std/io/util.ts";
-async function main(): Promise<void> {
+async function main() {
   for (let i = 1; i < Deno.args.length; i++) {
     const filename = Deno.args[i];
     const file = await Deno.open(filename);
diff --git a/cli/tests/complex_permissions_test.ts b/cli/tests/complex_permissions_test.ts
index 002d33540..bae157246 100644
--- a/cli/tests/complex_permissions_test.ts
+++ b/cli/tests/complex_permissions_test.ts
@@ -2,18 +2,18 @@
 const name = Deno.args[0];
 // deno-lint-ignore no-explicit-any
 const test: { [key: string]: (...args: any[]) => void | Promise<void> } = {
-  read(files: string[]): void {
+  read(files: string[]) {
     files.forEach((file) => Deno.readFileSync(file));
   },
-  write(files: string[]): void {
+  write(files: string[]) {
     files.forEach((file) =>
       Deno.writeFileSync(file, new Uint8Array(0), { append: true })
     );
   },
-  netFetch(urls: string[]): void {
+  netFetch(urls: string[]) {
     urls.forEach((url) => fetch(url));
   },
-  netListen(endpoints: string[]): void {
+  netListen(endpoints: string[]) {
     endpoints.forEach((endpoint) => {
       const index = endpoint.lastIndexOf(":");
       const [hostname, port] = [
@@ -28,7 +28,7 @@ const test: { [key: string]: (...args: any[]) => void | Promise<void> } = {
       listener.close();
     });
   },
-  async netConnect(endpoints: string[]): Promise<void> {
+  async netConnect(endpoints: string[]) {
     for (const endpoint of endpoints) {
       const index = endpoint.lastIndexOf(":");
       const [hostname, port] = [
diff --git a/cli/tests/echo.ts b/cli/tests/echo.ts
index bded2fd04..84a645433 100644
--- a/cli/tests/echo.ts
+++ b/cli/tests/echo.ts
@@ -1,4 +1,4 @@
-function echo(args: string[]): void {
+function echo(args: string[]) {
   const msg = args.join(", ");
   Deno.stdout.write(new TextEncoder().encode(msg));
 }
diff --git a/cli/tests/echo_server.ts b/cli/tests/echo_server.ts
index 7c8b0e42d..84284bea1 100644
--- a/cli/tests/echo_server.ts
+++ b/cli/tests/echo_server.ts
@@ -4,7 +4,7 @@ const [hostname, port] = addr.split(":");
 const listener = Deno.listen({ hostname, port: Number(port) });
 console.log("listening on", addr);
 listener.accept().then(
-  async (conn): Promise<void> => {
+  async (conn) => {
     console.log("received bytes:", await copy(conn, conn));
     conn.close();
     listener.close();
diff --git a/cli/tests/error_001.ts b/cli/tests/error_001.ts
index f06f80cb4..b01068bc0 100644
--- a/cli/tests/error_001.ts
+++ b/cli/tests/error_001.ts
@@ -2,7 +2,7 @@ function foo(): never {
   throw Error("bad");
 }
 
-function bar(): void {
+function bar() {
   foo();
 }
 
diff --git a/cli/tests/error_002.ts b/cli/tests/error_002.ts
index eb66764b7..6aa0fcc3b 100644
--- a/cli/tests/error_002.ts
+++ b/cli/tests/error_002.ts
@@ -1,6 +1,6 @@
 import { throwsError } from "./subdir/mod1.ts";
 
-function foo(): void {
+function foo() {
   throwsError();
 }
 
diff --git a/cli/tests/error_005_missing_dynamic_import.ts b/cli/tests/error_005_missing_dynamic_import.ts
index 4ff10f275..8ea8ff94e 100644
--- a/cli/tests/error_005_missing_dynamic_import.ts
+++ b/cli/tests/error_005_missing_dynamic_import.ts
@@ -1,3 +1,3 @@
-(async (): Promise<void> => {
+(async () => {
   const _badModule = await import("./bad-module.ts");
 })();
diff --git a/cli/tests/error_012_bad_dynamic_import_specifier.ts b/cli/tests/error_012_bad_dynamic_import_specifier.ts
index 1b538b787..5f39f407c 100644
--- a/cli/tests/error_012_bad_dynamic_import_specifier.ts
+++ b/cli/tests/error_012_bad_dynamic_import_specifier.ts
@@ -1,3 +1,3 @@
-(async (): Promise<void> => {
+(async () => {
   const _badModule = await import("bad-module.ts");
 })();
diff --git a/cli/tests/error_023_stack_async.ts b/cli/tests/error_023_stack_async.ts
index 621933576..99e676e26 100644
--- a/cli/tests/error_023_stack_async.ts
+++ b/cli/tests/error_023_stack_async.ts
@@ -1,4 +1,4 @@
-const p = (async (): Promise<void> => {
+const p = (async () => {
   await Promise.resolve().then((): never => {
     throw new Error("async");
   });
diff --git a/cli/tests/info_recursive_imports_test.ts b/cli/tests/info_recursive_imports_test.ts
index 0937bf4a5..c9ba44755 100644
--- a/cli/tests/info_recursive_imports_test.ts
+++ b/cli/tests/info_recursive_imports_test.ts
@@ -1,5 +1,5 @@
 import { A } from "./recursive_imports/A.ts";
 
-export function test(): void {
+export function test() {
   A();
 }
diff --git a/cli/tests/js_import_detect.ts b/cli/tests/js_import_detect.ts
index 7b90dfe63..751741996 100644
--- a/cli/tests/js_import_detect.ts
+++ b/cli/tests/js_import_detect.ts
@@ -1,3 +1,3 @@
-function define(_foo: string[]): void {}
+function define(_foo: string[]) {}
 define(["long"]);
 console.log("ok");
diff --git a/cli/tests/lock_check_err.json b/cli/tests/lock_check_err.json
index 55a1446d4..0a1380dfc 100644
--- a/cli/tests/lock_check_err.json
+++ b/cli/tests/lock_check_err.json
@@ -1,4 +1,4 @@
 {
-  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fe7bbccaedb6579200a8b582f905139296402d06b1b91109d6e12c41a23125da",
+  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fa6692c8f9ff3fb107e773c3ece5274e9d08be282867a1e3ded1d9c00fcaa63c",
   "http://127.0.0.1:4545/cli/tests/003_relative_import.ts": "bad"
 }
diff --git a/cli/tests/lock_check_err_with_bundle.json b/cli/tests/lock_check_err_with_bundle.json
index b773ed071..9c6a2e5f6 100644
--- a/cli/tests/lock_check_err_with_bundle.json
+++ b/cli/tests/lock_check_err_with_bundle.json
@@ -1,5 +1,5 @@
 {
-  "http://127.0.0.1:4545/cli/tests/subdir/mod1.ts": "bc699ebc05dec9a4baf2109258f03e6ec8dd5498e2f8c5469b62073b3b241657",
-  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fe7bbccaedb6579200a8b582f905139296402d06b1b91109d6e12c41a23125da",
+  "http://127.0.0.1:4545/cli/tests/subdir/mod1.ts": "bfc1037b02c99abc20367f739bca7455813a5950066abd77965bff33b6eece0f",
+  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fa6692c8f9ff3fb107e773c3ece5274e9d08be282867a1e3ded1d9c00fcaa63c",
   "http://127.0.0.1:4545/cli/tests/subdir/subdir2/mod2.ts": "bad"
 }
diff --git a/cli/tests/lock_check_ok.json b/cli/tests/lock_check_ok.json
index c4b68e158..e0ee0a17e 100644
--- a/cli/tests/lock_check_ok.json
+++ b/cli/tests/lock_check_ok.json
@@ -1,4 +1,4 @@
 {
-  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fe7bbccaedb6579200a8b582f905139296402d06b1b91109d6e12c41a23125da",
+  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fa6692c8f9ff3fb107e773c3ece5274e9d08be282867a1e3ded1d9c00fcaa63c",
   "http://127.0.0.1:4545/cli/tests/003_relative_import.ts": "aa9e16de824f81871a1c7164d5bd6857df7db2e18621750bd66b0bde4df07f21"
 }
diff --git a/cli/tests/lock_dynamic_imports.json b/cli/tests/lock_dynamic_imports.json
index bfc1cf7e7..fb822f64e 100644
--- a/cli/tests/lock_dynamic_imports.json
+++ b/cli/tests/lock_dynamic_imports.json
@@ -1,6 +1,6 @@
 {
-  "http://127.0.0.1:4545/cli/tests/013_dynamic_import.ts": "c875f10de49bded1ad76f1709d68e6cf2c0cfb8e8e862542a3fcb4ab09257b99",
-  "http://127.0.0.1:4545/cli/tests/subdir/mod1.ts": "bc699ebc05dec9a4baf2109258f03e6ec8dd5498e2f8c5469b62073b3b241657",
-  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fe7bbccaedb6579200a8b582f905139296402d06b1b91109d6e12c41a23125da",
+  "http://127.0.0.1:4545/cli/tests/013_dynamic_import.ts": "f0d2d108c100e769cda9f26b74326f21e44cab81611aa7f6cd2b731d4cbc1995",
+  "http://127.0.0.1:4545/cli/tests/subdir/mod1.ts": "bfc1037b02c99abc20367f739bca7455813a5950066abd77965bff33b6eece0f",
+  "http://127.0.0.1:4545/cli/tests/subdir/print_hello.ts": "fa6692c8f9ff3fb107e773c3ece5274e9d08be282867a1e3ded1d9c00fcaa63c",
   "http://127.0.0.1:4545/cli/tests/subdir/subdir2/mod2.ts": "bad"
 }
diff --git a/cli/tests/permission_test.ts b/cli/tests/permission_test.ts
index ac42b7d69..057e935af 100644
--- a/cli/tests/permission_test.ts
+++ b/cli/tests/permission_test.ts
@@ -2,20 +2,20 @@
 const name = Deno.args[0];
 // deno-lint-ignore no-explicit-any
 const test: { [key: string]: (...args: any[]) => void | Promise<void> } = {
-  readRequired(): Promise<void> {
+  readRequired() {
     Deno.readFileSync("README.md");
     return Promise.resolve();
   },
-  writeRequired(): void {
+  writeRequired() {
     Deno.makeTempDirSync();
   },
-  envRequired(): void {
+  envRequired() {
     Deno.env.get("home");
   },
-  netRequired(): void {
+  netRequired() {
     Deno.listen({ transport: "tcp", port: 4541 });
   },
-  runRequired(): void {
+  runRequired() {
     const p = Deno.run({
       cmd: Deno.build.os === "windows"
         ? ["cmd.exe", "/c", "echo hello"]
diff --git a/cli/tests/recursive_imports/A.ts b/cli/tests/recursive_imports/A.ts
index 04ef61581..43ecdbe5e 100644
--- a/cli/tests/recursive_imports/A.ts
+++ b/cli/tests/recursive_imports/A.ts
@@ -1,7 +1,7 @@
 import { B } from "./B.ts";
 import { thing } from "./common.ts";
 
-export function A(): void {
+export function A() {
   thing();
   B();
 }
diff --git a/cli/tests/recursive_imports/B.ts b/cli/tests/recursive_imports/B.ts
index a6e6917fd..9fff0fdc9 100644
--- a/cli/tests/recursive_imports/B.ts
+++ b/cli/tests/recursive_imports/B.ts
@@ -1,7 +1,7 @@
 import { C } from "./C.ts";
 import { thing } from "./common.ts";
 
-export function B(): void {
+export function B() {
   thing();
   C();
 }
diff --git a/cli/tests/recursive_imports/C.ts b/cli/tests/recursive_imports/C.ts
index be6ef9240..e47e77b41 100644
--- a/cli/tests/recursive_imports/C.ts
+++ b/cli/tests/recursive_imports/C.ts
@@ -1,7 +1,7 @@
 import { A } from "./A.ts";
 import { thing } from "./common.ts";
 
-export function C(): void {
+export function C() {
   if (A != null) {
     thing();
   }
diff --git a/cli/tests/recursive_imports/common.ts b/cli/tests/recursive_imports/common.ts
index d0f41395d..2b16a7bf1 100644
--- a/cli/tests/recursive_imports/common.ts
+++ b/cli/tests/recursive_imports/common.ts
@@ -1,2 +1,2 @@
-export function thing(): void {
+export function thing() {
 }
diff --git a/cli/tests/subdir/circular1.ts b/cli/tests/subdir/circular1.ts
index f9054338f..06fdb3373 100644
--- a/cli/tests/subdir/circular1.ts
+++ b/cli/tests/subdir/circular1.ts
@@ -1,6 +1,6 @@
 import * as circular2 from "./circular2.ts";
 
-export function f1(): void {
+export function f1() {
   console.log("f1");
 }
 
diff --git a/cli/tests/subdir/circular2.ts b/cli/tests/subdir/circular2.ts
index a96ffb13d..0864b7adf 100644
--- a/cli/tests/subdir/circular2.ts
+++ b/cli/tests/subdir/circular2.ts
@@ -1,6 +1,6 @@
 import * as circular1 from "./circular1.ts";
 
-export function f2(): void {
+export function f2() {
   console.log("f2");
 }
 
diff --git a/cli/tests/subdir/mod1.ts b/cli/tests/subdir/mod1.ts
index 9a4b53021..5e58f432e 100644
--- a/cli/tests/subdir/mod1.ts
+++ b/cli/tests/subdir/mod1.ts
@@ -8,10 +8,10 @@ export function returnsFoo2(): string {
   return returnsFoo();
 }
 
-export function printHello3(): void {
+export function printHello3() {
   printHello2();
 }
 
-export function throwsError(): void {
+export function throwsError() {
   throw Error("exception from mod1");
 }
diff --git a/cli/tests/subdir/print_hello.ts b/cli/tests/subdir/print_hello.ts
index 7ecce5040..b9c0ad527 100644
--- a/cli/tests/subdir/print_hello.ts
+++ b/cli/tests/subdir/print_hello.ts
@@ -1,3 +1,3 @@
-export function printHello(): void {
+export function printHello() {
   console.log("Hello");
 }
diff --git a/cli/tests/subdir/subdir2/dynamic_import.ts b/cli/tests/subdir/subdir2/dynamic_import.ts
index a8921390d..573887b71 100644
--- a/cli/tests/subdir/subdir2/dynamic_import.ts
+++ b/cli/tests/subdir/subdir2/dynamic_import.ts
@@ -1,4 +1,4 @@
-(async (): Promise<void> => {
+(async () => {
   const { printHello } = await import("../mod2.ts");
   printHello();
 })();
diff --git a/cli/tests/subdir/subdir2/mod2.ts b/cli/tests/subdir/subdir2/mod2.ts
index c88d4708c..9071d0aeb 100644
--- a/cli/tests/subdir/subdir2/mod2.ts
+++ b/cli/tests/subdir/subdir2/mod2.ts
@@ -4,6 +4,6 @@ export function returnsFoo(): string {
   return "Foo";
 }
 
-export function printHello2(): void {
+export function printHello2() {
   printHello();
 }
diff --git a/cli/tests/ts_decorators_bundle.ts b/cli/tests/ts_decorators_bundle.ts
index 189edfbff..72120b2ec 100644
--- a/cli/tests/ts_decorators_bundle.ts
+++ b/cli/tests/ts_decorators_bundle.ts
@@ -18,7 +18,7 @@ function Decorator() {
 
 class SomeClass {
   @Decorator()
-  async test(): Promise<void> {}
+  async test() {}
 }
 
 new SomeClass().test();
diff --git a/cli/tests/type_definitions_for_export.ts b/cli/tests/type_definitions_for_export.ts
index e9eb6b139..1f17b4962 100644
--- a/cli/tests/type_definitions_for_export.ts
+++ b/cli/tests/type_definitions_for_export.ts
@@ -1,6 +1,6 @@
 import { foo } from "./export_type_def.ts";
 
-function bar(a: number): void {
+function bar(a: number) {
   console.log(a);
 }
 
diff --git a/cli/tests/unit/abort_controller_test.ts b/cli/tests/unit/abort_controller_test.ts
index d89bcdd44..46c0e9394 100644
--- a/cli/tests/unit/abort_controller_test.ts
+++ b/cli/tests/unit/abort_controller_test.ts
@@ -14,7 +14,7 @@ unitTest(function signalCallsOnabort() {
   const controller = new AbortController();
   const { signal } = controller;
   let called = false;
-  signal.onabort = (evt): void => {
+  signal.onabort = (evt) => {
     assert(evt);
     assertEquals(evt.type, "abort");
     called = true;
@@ -41,7 +41,7 @@ unitTest(function onlyAbortsOnce() {
   const { signal } = controller;
   let called = 0;
   signal.addEventListener("abort", () => called++);
-  signal.onabort = (): void => {
+  signal.onabort = () => {
     called++;
   };
   controller.abort();
diff --git a/cli/tests/unit/blob_test.ts b/cli/tests/unit/blob_test.ts
index ebb91658a..8ce279160 100644
--- a/cli/tests/unit/blob_test.ts
+++ b/cli/tests/unit/blob_test.ts
@@ -7,14 +7,14 @@ import {
 } from "./test_util.ts";
 import { concat } from "../../../test_util/std/bytes/mod.ts";
 
-unitTest(function blobString(): void {
+unitTest(function blobString() {
   const b1 = new Blob(["Hello World"]);
   const str = "Test";
   const b2 = new Blob([b1, str]);
   assertEquals(b2.size, b1.size + str.length);
 });
 
-unitTest(function blobBuffer(): void {
+unitTest(function blobBuffer() {
   const buffer = new ArrayBuffer(12);
   const u8 = new Uint8Array(buffer);
   const f1 = new Float32Array(buffer);
@@ -24,7 +24,7 @@ unitTest(function blobBuffer(): void {
   assertEquals(b2.size, 3 * u8.length);
 });
 
-unitTest(function blobSlice(): void {
+unitTest(function blobSlice() {
   const blob = new Blob(["Deno", "Foo"]);
   const b1 = blob.slice(0, 3, "Text/HTML");
   assert(b1 instanceof Blob);
@@ -38,7 +38,7 @@ unitTest(function blobSlice(): void {
   assertEquals(b4.size, blob.size);
 });
 
-unitTest(function blobInvalidType(): void {
+unitTest(function blobInvalidType() {
   const blob = new Blob(["foo"], {
     type: "\u0521",
   });
@@ -46,7 +46,7 @@ unitTest(function blobInvalidType(): void {
   assertEquals(blob.type, "");
 });
 
-unitTest(function blobShouldNotThrowError(): void {
+unitTest(function blobShouldNotThrowError() {
   let hasThrown = false;
 
   try {
@@ -66,7 +66,7 @@ unitTest(function blobShouldNotThrowError(): void {
 });
 
 /* TODO https://github.com/denoland/deno/issues/7540
-unitTest(function nativeEndLine(): void {
+unitTest(function nativeEndLine() {
   const options = {
     ending: "native",
   } as const;
@@ -76,12 +76,12 @@ unitTest(function nativeEndLine(): void {
 });
 */
 
-unitTest(async function blobText(): Promise<void> {
+unitTest(async function blobText() {
   const blob = new Blob(["Hello World"]);
   assertEquals(await blob.text(), "Hello World");
 });
 
-unitTest(async function blobStream(): Promise<void> {
+unitTest(async function blobStream() {
   const blob = new Blob(["Hello World"]);
   const stream = blob.stream();
   assert(stream instanceof ReadableStream);
@@ -99,18 +99,18 @@ unitTest(async function blobStream(): Promise<void> {
   assertEquals(decoder.decode(bytes), "Hello World");
 });
 
-unitTest(async function blobArrayBuffer(): Promise<void> {
+unitTest(async function blobArrayBuffer() {
   const uint = new Uint8Array([102, 111, 111]);
   const blob = new Blob([uint]);
   assertEquals(await blob.arrayBuffer(), uint.buffer);
 });
 
-unitTest(function blobConstructorNameIsBlob(): void {
+unitTest(function blobConstructorNameIsBlob() {
   const blob = new Blob();
   assertEquals(blob.constructor.name, "Blob");
 });
 
-unitTest(function blobCustomInspectFunction(): void {
+unitTest(function blobCustomInspectFunction() {
   const blob = new Blob();
   assertEquals(
     Deno.inspect(blob),
diff --git a/cli/tests/unit/body_test.ts b/cli/tests/unit/body_test.ts
index d889abfab..78da2a9d4 100644
--- a/cli/tests/unit/body_test.ts
+++ b/cli/tests/unit/body_test.ts
@@ -23,7 +23,7 @@ const intArrays = [
   Float32Array,
   Float64Array,
 ];
-unitTest(async function arrayBufferFromByteArrays(): Promise<void> {
+unitTest(async function arrayBufferFromByteArrays() {
   const buffer = new TextEncoder().encode("ahoyhoy8").buffer;
 
   for (const type of intArrays) {
@@ -36,7 +36,7 @@ unitTest(async function arrayBufferFromByteArrays(): Promise<void> {
 //FormData
 unitTest(
   { perms: { net: true } },
-  async function bodyMultipartFormData(): Promise<void> {
+  async function bodyMultipartFormData() {
     const response = await fetch(
       "http://localhost:4545/multipart_form_data.txt",
     );
@@ -55,7 +55,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function bodyURLEncodedFormData(): Promise<void> {
+  async function bodyURLEncodedFormData() {
     const response = await fetch(
       "http://localhost:4545/cli/tests/subdir/form_urlencoded.txt",
     );
@@ -73,14 +73,14 @@ unitTest(
   },
 );
 
-unitTest({ perms: {} }, async function bodyURLSearchParams(): Promise<void> {
+unitTest({ perms: {} }, async function bodyURLSearchParams() {
   const body = buildBody(new URLSearchParams({ hello: "world" }));
 
   const text = await body.text();
   assertEquals(text, "hello=world");
 });
 
-unitTest(async function bodyArrayBufferMultipleParts(): Promise<void> {
+unitTest(async function bodyArrayBufferMultipleParts() {
   const parts: Uint8Array[] = [];
   let size = 0;
   for (let i = 0; i <= 150000; i++) {
@@ -91,7 +91,7 @@ unitTest(async function bodyArrayBufferMultipleParts(): Promise<void> {
 
   let offset = 0;
   const stream = new ReadableStream({
-    pull(controller): void {
+    pull(controller) {
       // parts.shift() takes forever: https://github.com/denoland/deno/issues/5259
       const chunk = parts[offset++];
       if (!chunk) return controller.close();
diff --git a/cli/tests/unit/buffer_test.ts b/cli/tests/unit/buffer_test.ts
index 57476e0f3..30198d0b9 100644
--- a/cli/tests/unit/buffer_test.ts
+++ b/cli/tests/unit/buffer_test.ts
@@ -21,7 +21,7 @@ let testString: string | null;
 
 const ignoreMaxSizeTests = true;
 
-function init(): void {
+function init() {
   if (testBytes == null) {
     testBytes = new Uint8Array(N);
     for (let i = 0; i < N; i++) {
@@ -32,7 +32,7 @@ function init(): void {
   }
 }
 
-function check(buf: Deno.Buffer, s: string): void {
+function check(buf: Deno.Buffer, s: string) {
   const bytes = buf.bytes();
   assertEquals(buf.length, bytes.byteLength);
   const decoder = new TextDecoder();
@@ -67,7 +67,7 @@ async function empty(
   buf: Deno.Buffer,
   s: string,
   fub: Uint8Array,
-): Promise<void> {
+) {
   check(buf, s);
   while (true) {
     const r = await buf.read(fub);
@@ -87,7 +87,7 @@ function repeat(c: string, bytes: number): Uint8Array {
   return ui8;
 }
 
-unitTest(function bufferNewBuffer(): void {
+unitTest(function bufferNewBuffer() {
   init();
   assert(testBytes);
   assert(testString);
@@ -95,7 +95,7 @@ unitTest(function bufferNewBuffer(): void {
   check(buf, testString);
 });
 
-unitTest(async function bufferBasicOperations(): Promise<void> {
+unitTest(async function bufferBasicOperations() {
   init();
   assert(testBytes);
   assert(testString);
@@ -135,7 +135,7 @@ unitTest(async function bufferBasicOperations(): Promise<void> {
   }
 });
 
-unitTest(async function bufferReadEmptyAtEOF(): Promise<void> {
+unitTest(async function bufferReadEmptyAtEOF() {
   // check that EOF of 'buf' is not reached (even though it's empty) if
   // results are written to buffer that has 0 length (ie. it can't store any data)
   const buf = new Deno.Buffer();
@@ -144,7 +144,7 @@ unitTest(async function bufferReadEmptyAtEOF(): Promise<void> {
   assertEquals(result, 0);
 });
 
-unitTest(async function bufferLargeByteWrites(): Promise<void> {
+unitTest(async function bufferLargeByteWrites() {
   init();
   const buf = new Deno.Buffer();
   const limit = 9;
@@ -155,7 +155,7 @@ unitTest(async function bufferLargeByteWrites(): Promise<void> {
   check(buf, "");
 });
 
-unitTest(async function bufferTooLargeByteWrites(): Promise<void> {
+unitTest(async function bufferTooLargeByteWrites() {
   init();
   const tmp = new Uint8Array(72);
   const growLen = Number.MAX_VALUE;
@@ -174,7 +174,7 @@ unitTest(async function bufferTooLargeByteWrites(): Promise<void> {
 
 unitTest(
   { ignore: ignoreMaxSizeTests },
-  function bufferGrowWriteMaxBuffer(): void {
+  function bufferGrowWriteMaxBuffer() {
     const bufSize = 16 * 1024;
     const capacities = [MAX_SIZE, MAX_SIZE - 1];
     for (const capacity of capacities) {
@@ -196,7 +196,7 @@ unitTest(
 
 unitTest(
   { ignore: ignoreMaxSizeTests },
-  async function bufferGrowReadCloseMaxBufferPlus1(): Promise<void> {
+  async function bufferGrowReadCloseMaxBufferPlus1() {
     const reader = new Deno.Buffer(new ArrayBuffer(MAX_SIZE + 1));
     const buf = new Deno.Buffer();
 
@@ -212,7 +212,7 @@ unitTest(
 
 unitTest(
   { ignore: ignoreMaxSizeTests },
-  function bufferGrowReadSyncCloseMaxBufferPlus1(): void {
+  function bufferGrowReadSyncCloseMaxBufferPlus1() {
     const reader = new Deno.Buffer(new ArrayBuffer(MAX_SIZE + 1));
     const buf = new Deno.Buffer();
 
@@ -228,7 +228,7 @@ unitTest(
 
 unitTest(
   { ignore: ignoreMaxSizeTests },
-  function bufferGrowReadSyncCloseToMaxBuffer(): void {
+  function bufferGrowReadSyncCloseToMaxBuffer() {
     const capacities = [MAX_SIZE, MAX_SIZE - 1];
     for (const capacity of capacities) {
       const reader = new Deno.Buffer(new ArrayBuffer(capacity));
@@ -242,7 +242,7 @@ unitTest(
 
 unitTest(
   { ignore: ignoreMaxSizeTests },
-  async function bufferGrowReadCloseToMaxBuffer(): Promise<void> {
+  async function bufferGrowReadCloseToMaxBuffer() {
     const capacities = [MAX_SIZE, MAX_SIZE - 1];
     for (const capacity of capacities) {
       const reader = new Deno.Buffer(new ArrayBuffer(capacity));
@@ -255,7 +255,7 @@ unitTest(
 
 unitTest(
   { ignore: ignoreMaxSizeTests },
-  async function bufferReadCloseToMaxBufferWithInitialGrow(): Promise<void> {
+  async function bufferReadCloseToMaxBufferWithInitialGrow() {
     const capacities = [MAX_SIZE, MAX_SIZE - 1, MAX_SIZE - 512];
     for (const capacity of capacities) {
       const reader = new Deno.Buffer(new ArrayBuffer(capacity));
@@ -267,7 +267,7 @@ unitTest(
   },
 );
 
-unitTest(async function bufferLargeByteReads(): Promise<void> {
+unitTest(async function bufferLargeByteReads() {
   init();
   assert(testBytes);
   assert(testString);
@@ -280,12 +280,12 @@ unitTest(async function bufferLargeByteReads(): Promise<void> {
   check(buf, "");
 });
 
-unitTest(function bufferCapWithPreallocatedSlice(): void {
+unitTest(function bufferCapWithPreallocatedSlice() {
   const buf = new Deno.Buffer(new ArrayBuffer(10));
   assertEquals(buf.capacity, 10);
 });
 
-unitTest(async function bufferReadFrom(): Promise<void> {
+unitTest(async function bufferReadFrom() {
   init();
   assert(testBytes);
   assert(testString);
@@ -307,7 +307,7 @@ unitTest(async function bufferReadFrom(): Promise<void> {
   });
 });
 
-unitTest(async function bufferReadFromSync(): Promise<void> {
+unitTest(async function bufferReadFromSync() {
   init();
   assert(testBytes);
   assert(testString);
@@ -329,7 +329,7 @@ unitTest(async function bufferReadFromSync(): Promise<void> {
   });
 });
 
-unitTest(async function bufferTestGrow(): Promise<void> {
+unitTest(async function bufferTestGrow() {
   const tmp = new Uint8Array(72);
   for (const startLen of [0, 100, 1000, 10000]) {
     const xBytes = repeat("x", startLen);
@@ -353,7 +353,7 @@ unitTest(async function bufferTestGrow(): Promise<void> {
   }
 });
 
-unitTest(async function testReadAll(): Promise<void> {
+unitTest(async function testReadAll() {
   init();
   assert(testBytes);
   const reader = new Deno.Buffer(testBytes.buffer as ArrayBuffer);
@@ -364,7 +364,7 @@ unitTest(async function testReadAll(): Promise<void> {
   }
 });
 
-unitTest(function testReadAllSync(): void {
+unitTest(function testReadAllSync() {
   init();
   assert(testBytes);
   const reader = new Deno.Buffer(testBytes.buffer as ArrayBuffer);
@@ -375,7 +375,7 @@ unitTest(function testReadAllSync(): void {
   }
 });
 
-unitTest(async function testWriteAll(): Promise<void> {
+unitTest(async function testWriteAll() {
   init();
   assert(testBytes);
   const writer = new Deno.Buffer();
@@ -387,7 +387,7 @@ unitTest(async function testWriteAll(): Promise<void> {
   }
 });
 
-unitTest(function testWriteAllSync(): void {
+unitTest(function testWriteAllSync() {
   init();
   assert(testBytes);
   const writer = new Deno.Buffer();
@@ -399,7 +399,7 @@ unitTest(function testWriteAllSync(): void {
   }
 });
 
-unitTest(function testBufferBytesArrayBufferLength(): void {
+unitTest(function testBufferBytesArrayBufferLength() {
   // defaults to copy
   const args = [{}, { copy: undefined }, undefined, { copy: true }];
   for (const arg of args) {
@@ -418,7 +418,7 @@ unitTest(function testBufferBytesArrayBufferLength(): void {
   }
 });
 
-unitTest(function testBufferBytesCopyFalse(): void {
+unitTest(function testBufferBytesCopyFalse() {
   const bufSize = 64 * 1024;
   const bytes = new TextEncoder().encode("a".repeat(bufSize));
   const reader = new Deno.Buffer();
@@ -433,7 +433,7 @@ unitTest(function testBufferBytesCopyFalse(): void {
   assert(actualBytes.buffer.byteLength > actualBytes.byteLength);
 });
 
-unitTest(function testBufferBytesCopyFalseGrowExactBytes(): void {
+unitTest(function testBufferBytesCopyFalseGrowExactBytes() {
   const bufSize = 64 * 1024;
   const bytes = new TextEncoder().encode("a".repeat(bufSize));
   const reader = new Deno.Buffer();
diff --git a/cli/tests/unit/build_test.ts b/cli/tests/unit/build_test.ts
index 731290326..01027d4f1 100644
--- a/cli/tests/unit/build_test.ts
+++ b/cli/tests/unit/build_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, unitTest } from "./test_util.ts";
 
-unitTest(function buildInfo(): void {
+unitTest(function buildInfo() {
   // Deno.build is injected by rollup at compile time. Here
   // we check it has been properly transformed.
   const { arch, os } = Deno.build;
diff --git a/cli/tests/unit/chmod_test.ts b/cli/tests/unit/chmod_test.ts
index 80f240134..5908ea09a 100644
--- a/cli/tests/unit/chmod_test.ts
+++ b/cli/tests/unit/chmod_test.ts
@@ -9,7 +9,7 @@ import {
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  function chmodSyncSuccess(): void {
+  function chmodSyncSuccess() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -26,7 +26,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  function chmodSyncUrl(): void {
+  function chmodSyncUrl() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -49,7 +49,7 @@ unitTest(
     ignore: Deno.build.os === "windows",
     perms: { read: true, write: true },
   },
-  function chmodSyncSymlinkSuccess(): void {
+  function chmodSyncSymlinkSuccess() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -75,14 +75,14 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: true } }, function chmodSyncFailure(): void {
+unitTest({ perms: { write: true } }, function chmodSyncFailure() {
   assertThrows(() => {
     const filename = "/badfile.txt";
     Deno.chmodSync(filename, 0o777);
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { write: false } }, function chmodSyncPerm(): void {
+unitTest({ perms: { write: false } }, function chmodSyncPerm() {
   assertThrows(() => {
     Deno.chmodSync("/somefile.txt", 0o777);
   }, Deno.errors.PermissionDenied);
@@ -90,7 +90,7 @@ unitTest({ perms: { write: false } }, function chmodSyncPerm(): void {
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function chmodSuccess(): Promise<void> {
+  async function chmodSuccess() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -107,7 +107,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function chmodUrl(): Promise<void> {
+  async function chmodUrl() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -131,7 +131,7 @@ unitTest(
     ignore: Deno.build.os === "windows",
     perms: { read: true, write: true },
   },
-  async function chmodSymlinkSuccess(): Promise<void> {
+  async function chmodSymlinkSuccess() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -157,18 +157,14 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: true } }, async function chmodFailure(): Promise<
-  void
-> {
+unitTest({ perms: { write: true } }, async function chmodFailure() {
   await assertThrowsAsync(async () => {
     const filename = "/badfile.txt";
     await Deno.chmod(filename, 0o777);
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { write: false } }, async function chmodPerm(): Promise<
-  void
-> {
+unitTest({ perms: { write: false } }, async function chmodPerm() {
   await assertThrowsAsync(async () => {
     await Deno.chmod("/somefile.txt", 0o777);
   }, Deno.errors.PermissionDenied);
diff --git a/cli/tests/unit/chown_test.ts b/cli/tests/unit/chown_test.ts
index 2fac679ce..a8d264a6c 100644
--- a/cli/tests/unit/chown_test.ts
+++ b/cli/tests/unit/chown_test.ts
@@ -31,7 +31,7 @@ async function getUidAndGid(): Promise<{ uid: number; gid: number }> {
 
 unitTest(
   { ignore: Deno.build.os == "windows" },
-  async function chownNoWritePermission(): Promise<void> {
+  async function chownNoWritePermission() {
     const filePath = "chown_test_file.txt";
     await assertThrowsAsync(async () => {
       await Deno.chown(filePath, 1000, 1000);
@@ -41,7 +41,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownSyncFileNotExist(): Promise<void> {
+  async function chownSyncFileNotExist() {
     const { uid, gid } = await getUidAndGid();
     const filePath = Deno.makeTempDirSync() + "/chown_test_file.txt";
 
@@ -53,7 +53,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownFileNotExist(): Promise<void> {
+  async function chownFileNotExist() {
     const { uid, gid } = await getUidAndGid();
     const filePath = (await Deno.makeTempDir()) + "/chown_test_file.txt";
 
@@ -65,7 +65,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true }, ignore: Deno.build.os == "windows" },
-  function chownSyncPermissionDenied(): void {
+  function chownSyncPermissionDenied() {
     const dirPath = Deno.makeTempDirSync();
     const filePath = dirPath + "/chown_test_file.txt";
     Deno.writeTextFileSync(filePath, "Hello");
@@ -80,7 +80,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true }, ignore: Deno.build.os == "windows" },
-  async function chownPermissionDenied(): Promise<void> {
+  async function chownPermissionDenied() {
     const dirPath = await Deno.makeTempDir();
     const filePath = dirPath + "/chown_test_file.txt";
     await Deno.writeTextFile(filePath, "Hello");
@@ -95,7 +95,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownSyncSucceed(): Promise<void> {
+  async function chownSyncSucceed() {
     // TODO(bartlomieju): when a file's owner is actually being changed,
     // chown only succeeds if run under priviledged user (root)
     // The test script has no such privilege, so need to find a better way to test this case
@@ -115,7 +115,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownSyncWithUrl(): Promise<void> {
+  async function chownSyncWithUrl() {
     const { uid, gid } = await getUidAndGid();
     const dirPath = Deno.makeTempDirSync();
     const fileUrl = new URL(`file://${dirPath}/chown_test_file.txt`);
@@ -127,7 +127,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownSucceed(): Promise<void> {
+  async function chownSucceed() {
     const { uid, gid } = await getUidAndGid();
     const dirPath = await Deno.makeTempDir();
     const filePath = dirPath + "/chown_test_file.txt";
@@ -139,7 +139,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownUidOnly(): Promise<void> {
+  async function chownUidOnly() {
     const { uid } = await getUidAndGid();
     const dirPath = await Deno.makeTempDir();
     const filePath = dirPath + "/chown_test_file.txt";
@@ -151,7 +151,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true }, ignore: Deno.build.os == "windows" },
-  async function chownWithUrl(): Promise<void> {
+  async function chownWithUrl() {
     // TODO(bartlomieju): same as chownSyncSucceed
     const { uid, gid } = await getUidAndGid();
 
diff --git a/cli/tests/unit/console_test.ts b/cli/tests/unit/console_test.ts
index 0fb75c89f..3d34c83ce 100644
--- a/cli/tests/unit/console_test.ts
+++ b/cli/tests/unit/console_test.ts
@@ -64,7 +64,7 @@ function cssToAnsiEsc(css: Css, prevCss: Css | null = null): string {
 
 // test cases from web-platform-tests
 // via https://github.com/web-platform-tests/wpt/blob/master/console/console-is-a-namespace.any.js
-unitTest(function consoleShouldBeANamespace(): void {
+unitTest(function consoleShouldBeANamespace() {
   const prototype1 = Object.getPrototypeOf(console);
   const prototype2 = Object.getPrototypeOf(prototype1);
 
@@ -72,12 +72,12 @@ unitTest(function consoleShouldBeANamespace(): void {
   assertEquals(prototype2, Object.prototype);
 });
 
-unitTest(function consoleHasRightInstance(): void {
+unitTest(function consoleHasRightInstance() {
   assert(console instanceof Console);
   assertEquals({} instanceof Console, false);
 });
 
-unitTest(function consoleTestAssertShouldNotThrowError(): void {
+unitTest(function consoleTestAssertShouldNotThrowError() {
   mockConsole((console) => {
     console.assert(true);
     let hasThrown = undefined;
@@ -91,14 +91,14 @@ unitTest(function consoleTestAssertShouldNotThrowError(): void {
   });
 });
 
-unitTest(function consoleTestStringifyComplexObjects(): void {
+unitTest(function consoleTestStringifyComplexObjects() {
   assertEquals(stringify("foo"), "foo");
   assertEquals(stringify(["foo", "bar"]), `[ "foo", "bar" ]`);
   assertEquals(stringify({ foo: "bar" }), `{ foo: "bar" }`);
 });
 
 unitTest(
-  function consoleTestStringifyComplexObjectsWithEscapedSequences(): void {
+  function consoleTestStringifyComplexObjectsWithEscapedSequences() {
     assertEquals(
       stringify(
         ["foo\b", "foo\f", "foo\n", "foo\r", "foo\t", "foo\v", "foo\0"],
@@ -167,14 +167,14 @@ unitTest(
   },
 );
 
-unitTest(function consoleTestStringifyQuotes(): void {
+unitTest(function consoleTestStringifyQuotes() {
   assertEquals(stringify(["\\"]), `[ "\\\\" ]`);
   assertEquals(stringify(['\\,"']), `[ '\\\\,"' ]`);
   assertEquals(stringify([`\\,",'`]), `[ \`\\\\,",'\` ]`);
   assertEquals(stringify(["\\,\",',`"]), `[ "\\\\,\\",',\`" ]`);
 });
 
-unitTest(function consoleTestStringifyLongStrings(): void {
+unitTest(function consoleTestStringifyLongStrings() {
   const veryLongString = "a".repeat(200);
   // If we stringify an object containing the long string, it gets abbreviated.
   let actual = stringify({ veryLongString });
@@ -185,7 +185,7 @@ unitTest(function consoleTestStringifyLongStrings(): void {
   assertEquals(actual, veryLongString);
 });
 
-unitTest(function consoleTestStringifyCircular(): void {
+unitTest(function consoleTestStringifyCircular() {
   class Base {
     a = 1;
     m1() {}
@@ -283,11 +283,11 @@ unitTest(function consoleTestStringifyCircular(): void {
   assertEquals(stringify(undefined), "undefined");
   assertEquals(stringify(new Extended()), "Extended { a: 1, b: 2 }");
   assertEquals(
-    stringify(function f(): void {}),
+    stringify(function f() {}),
     "[Function: f]",
   );
   assertEquals(
-    stringify(async function af(): Promise<void> {}),
+    stringify(async function af() {}),
     "[AsyncFunction: af]",
   );
   assertEquals(
@@ -354,7 +354,7 @@ unitTest(function consoleTestStringifyCircular(): void {
   assertEquals(stripColor(Deno.inspect(nestedObj)), nestedObjExpected);
 });
 
-unitTest(function consoleTestStringifyFunctionWithPrototypeRemoved(): void {
+unitTest(function consoleTestStringifyFunctionWithPrototypeRemoved() {
   const f = function f() {};
   Reflect.setPrototypeOf(f, null);
   assertEquals(stringify(f), "[Function: f]");
@@ -369,7 +369,7 @@ unitTest(function consoleTestStringifyFunctionWithPrototypeRemoved(): void {
   assertEquals(stringify(agf), "[Function: agf]");
 });
 
-unitTest(function consoleTestStringifyFunctionWithProperties(): void {
+unitTest(function consoleTestStringifyFunctionWithProperties() {
   const f = () => "test";
   f.x = () => "foo";
   f.y = 3;
@@ -413,7 +413,7 @@ unitTest(function consoleTestStringifyFunctionWithProperties(): void {
   );
 });
 
-unitTest(function consoleTestStringifyWithDepth(): void {
+unitTest(function consoleTestStringifyWithDepth() {
   // deno-lint-ignore no-explicit-any
   const nestedObj: any = { a: { b: { c: { d: { e: { f: 42 } } } } } };
   assertEquals(
@@ -436,7 +436,7 @@ unitTest(function consoleTestStringifyWithDepth(): void {
   );
 });
 
-unitTest(function consoleTestStringifyLargeObject(): void {
+unitTest(function consoleTestStringifyLargeObject() {
   const obj = {
     a: 2,
     o: {
@@ -768,7 +768,7 @@ unitTest(function consoleTestStringifyIterable() {
   */
 });
 
-unitTest(function consoleTestStringifyIterableWhenGrouped(): void {
+unitTest(function consoleTestStringifyIterableWhenGrouped() {
   const withOddNumberOfEls = new Float64Array(
     [
       2.1,
@@ -846,7 +846,7 @@ unitTest(function consoleTestStringifyIterableWhenGrouped(): void {
   );
 });
 
-unitTest(async function consoleTestStringifyPromises(): Promise<void> {
+unitTest(async function consoleTestStringifyPromises() {
   const pendingPromise = new Promise((_res, _rej) => {});
   assertEquals(stringify(pendingPromise), "Promise { <pending> }");
 
@@ -869,7 +869,7 @@ unitTest(async function consoleTestStringifyPromises(): Promise<void> {
   assertEquals(strLines[1], "  <rejected> Error: Whoops");
 });
 
-unitTest(function consoleTestWithCustomInspector(): void {
+unitTest(function consoleTestWithCustomInspector() {
   class A {
     [customInspect](): string {
       return "b";
@@ -879,7 +879,7 @@ unitTest(function consoleTestWithCustomInspector(): void {
   assertEquals(stringify(new A()), "b");
 });
 
-unitTest(function consoleTestWithCustomInspectorUsingInspectFunc(): void {
+unitTest(function consoleTestWithCustomInspectorUsingInspectFunc() {
   class A {
     [customInspect](
       inspect: (v: unknown, opts?: Deno.InspectOptions) => string,
@@ -891,7 +891,7 @@ unitTest(function consoleTestWithCustomInspectorUsingInspectFunc(): void {
   assertEquals(stringify(new A()), "b { c: 1 }");
 });
 
-unitTest(function consoleTestWithCustomInspectorError(): void {
+unitTest(function consoleTestWithCustomInspectorError() {
   class A {
     [customInspect](): never {
       throw new Error("BOOM");
@@ -913,7 +913,7 @@ unitTest(function consoleTestWithCustomInspectorError(): void {
   );
 });
 
-unitTest(function consoleTestWithCustomInspectFunction(): void {
+unitTest(function consoleTestWithCustomInspectFunction() {
   function a() {}
   Object.assign(a, {
     [customInspect]() {
@@ -924,7 +924,7 @@ unitTest(function consoleTestWithCustomInspectFunction(): void {
   assertEquals(stringify(a), "b");
 });
 
-unitTest(function consoleTestWithIntegerFormatSpecifier(): void {
+unitTest(function consoleTestWithIntegerFormatSpecifier() {
   assertEquals(stringify("%i"), "%i");
   assertEquals(stringify("%i", 42.0), "42");
   assertEquals(stringify("%i", 42), "42");
@@ -942,7 +942,7 @@ unitTest(function consoleTestWithIntegerFormatSpecifier(): void {
   );
 });
 
-unitTest(function consoleTestWithFloatFormatSpecifier(): void {
+unitTest(function consoleTestWithFloatFormatSpecifier() {
   assertEquals(stringify("%f"), "%f");
   assertEquals(stringify("%f", 42.0), "42");
   assertEquals(stringify("%f", 42), "42");
@@ -957,7 +957,7 @@ unitTest(function consoleTestWithFloatFormatSpecifier(): void {
   assertEquals(stringify("%f %f", 42), "42 %f");
 });
 
-unitTest(function consoleTestWithStringFormatSpecifier(): void {
+unitTest(function consoleTestWithStringFormatSpecifier() {
   assertEquals(stringify("%s"), "%s");
   assertEquals(stringify("%s", undefined), "undefined");
   assertEquals(stringify("%s", "foo"), "foo");
@@ -968,7 +968,7 @@ unitTest(function consoleTestWithStringFormatSpecifier(): void {
   assertEquals(stringify("%s", Symbol("foo")), "Symbol(foo)");
 });
 
-unitTest(function consoleTestWithObjectFormatSpecifier(): void {
+unitTest(function consoleTestWithObjectFormatSpecifier() {
   assertEquals(stringify("%o"), "%o");
   assertEquals(stringify("%o", 42), "42");
   assertEquals(stringify("%o", "foo"), `"foo"`);
@@ -980,13 +980,13 @@ unitTest(function consoleTestWithObjectFormatSpecifier(): void {
   );
 });
 
-unitTest(function consoleTestWithStyleSpecifier(): void {
+unitTest(function consoleTestWithStyleSpecifier() {
   assertEquals(stringify("%cfoo%cbar"), "%cfoo%cbar");
   assertEquals(stringify("%cfoo%cbar", ""), "foo%cbar");
   assertEquals(stripColor(stringify("%cfoo%cbar", "", "color: red")), "foobar");
 });
 
-unitTest(function consoleParseCssColor(): void {
+unitTest(function consoleParseCssColor() {
   assertEquals(parseCssColor("black"), [0, 0, 0]);
   assertEquals(parseCssColor("darkmagenta"), [139, 0, 139]);
   assertEquals(parseCssColor("slateblue"), [106, 90, 205]);
@@ -1005,7 +1005,7 @@ unitTest(function consoleParseCssColor(): void {
   );
 });
 
-unitTest(function consoleParseCss(): void {
+unitTest(function consoleParseCss() {
   assertEquals(
     parseCss("background-color: red"),
     { ...DEFAULT_CSS, backgroundColor: [255, 0, 0] },
@@ -1059,7 +1059,7 @@ unitTest(function consoleParseCss(): void {
   );
 });
 
-unitTest(function consoleCssToAnsi(): void {
+unitTest(function consoleCssToAnsi() {
   assertEquals(
     cssToAnsiEsc({ ...DEFAULT_CSS, backgroundColor: [200, 201, 202] }),
     "_[48;2;200;201;202m",
@@ -1099,7 +1099,7 @@ unitTest(function consoleCssToAnsi(): void {
   );
 });
 
-unitTest(function consoleTestWithVariousOrInvalidFormatSpecifier(): void {
+unitTest(function consoleTestWithVariousOrInvalidFormatSpecifier() {
   assertEquals(stringify("%s:%s"), "%s:%s");
   assertEquals(stringify("%i:%i"), "%i:%i");
   assertEquals(stringify("%d:%d"), "%d:%d");
@@ -1115,13 +1115,13 @@ unitTest(function consoleTestWithVariousOrInvalidFormatSpecifier(): void {
   assertEquals(stringify("abc%", 1), "abc% 1");
 });
 
-unitTest(function consoleTestCallToStringOnLabel(): void {
+unitTest(function consoleTestCallToStringOnLabel() {
   const methods = ["count", "countReset", "time", "timeLog", "timeEnd"];
   mockConsole((console) => {
     for (const method of methods) {
       let hasCalled = false;
       console[method]({
-        toString(): void {
+        toString() {
           hasCalled = true;
         },
       });
@@ -1130,7 +1130,7 @@ unitTest(function consoleTestCallToStringOnLabel(): void {
   });
 });
 
-unitTest(function consoleTestError(): void {
+unitTest(function consoleTestError() {
   class MyError extends Error {
     constructor(errStr: string) {
       super(errStr);
@@ -1148,7 +1148,7 @@ unitTest(function consoleTestError(): void {
   }
 });
 
-unitTest(function consoleTestClear(): void {
+unitTest(function consoleTestClear() {
   mockConsole((console, out) => {
     console.clear();
     assertEquals(out.toString(), "\x1b[1;1H" + "\x1b[0J");
@@ -1156,7 +1156,7 @@ unitTest(function consoleTestClear(): void {
 });
 
 // Test bound this issue
-unitTest(function consoleDetachedLog(): void {
+unitTest(function consoleDetachedLog() {
   mockConsole((console) => {
     const log = console.log;
     const dir = console.dir;
@@ -1197,7 +1197,7 @@ unitTest(function consoleDetachedLog(): void {
 
 class StringBuffer {
   chunks: string[] = [];
-  add(x: string): void {
+  add(x: string) {
     this.chunks.push(x);
   }
   toString(): string {
@@ -1213,12 +1213,12 @@ type ConsoleExamineFunc = (
   both?: StringBuffer,
 ) => void;
 
-function mockConsole(f: ConsoleExamineFunc): void {
+function mockConsole(f: ConsoleExamineFunc) {
   const out = new StringBuffer();
   const err = new StringBuffer();
   const both = new StringBuffer();
   const csl = new Console(
-    (x: string, level: number, printsNewLine: boolean): void => {
+    (x: string, level: number, printsNewLine: boolean) => {
       const content = x + (printsNewLine ? "\n" : "");
       const buf = level > 1 ? err : out;
       buf.add(content);
@@ -1229,8 +1229,8 @@ function mockConsole(f: ConsoleExamineFunc): void {
 }
 
 // console.group test
-unitTest(function consoleGroup(): void {
-  mockConsole((console, out): void => {
+unitTest(function consoleGroup() {
+  mockConsole((console, out) => {
     console.group("1");
     console.log("2");
     console.group("3");
@@ -1254,8 +1254,8 @@ unitTest(function consoleGroup(): void {
 });
 
 // console.group with console.warn test
-unitTest(function consoleGroupWarn(): void {
-  mockConsole((console, _out, _err, both): void => {
+unitTest(function consoleGroupWarn() {
+  mockConsole((console, _out, _err, both) => {
     assert(both);
     console.warn("1");
     console.group();
@@ -1284,8 +1284,8 @@ unitTest(function consoleGroupWarn(): void {
 });
 
 // console.table test
-unitTest(function consoleTable(): void {
-  mockConsole((console, out): void => {
+unitTest(function consoleTable() {
+  mockConsole((console, out) => {
     console.table({ a: "test", b: 1 });
     assertEquals(
       stripColor(out.toString()),
@@ -1298,7 +1298,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table({ a: { b: 10 }, b: { b: 20, c: 30 } }, ["c"]);
     assertEquals(
       stripColor(out.toString()),
@@ -1311,7 +1311,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table([1, 2, [3, [4]], [5, 6], [[7], [8]]]);
     assertEquals(
       stripColor(out.toString()),
@@ -1327,7 +1327,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table(new Set([1, 2, 3, "test"]));
     assertEquals(
       stripColor(out.toString()),
@@ -1342,7 +1342,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table(
       new Map([
         [1, "one"],
@@ -1360,7 +1360,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table({
       a: true,
       b: { c: { d: 10 }, e: [1, 2, [5, 6]] },
@@ -1382,7 +1382,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table([
       1,
       "test",
@@ -1404,7 +1404,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table([]);
     assertEquals(
       stripColor(out.toString()),
@@ -1415,7 +1415,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table({});
     assertEquals(
       stripColor(out.toString()),
@@ -1426,7 +1426,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table(new Set());
     assertEquals(
       stripColor(out.toString()),
@@ -1437,7 +1437,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table(new Map());
     assertEquals(
       stripColor(out.toString()),
@@ -1448,11 +1448,11 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table("test");
     assertEquals(out.toString(), "test\n");
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table(["Hello", "你好", "Amapá"]);
     assertEquals(
       stripColor(out.toString()),
@@ -1466,7 +1466,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table([
       [1, 2],
       [3, 4],
@@ -1482,7 +1482,7 @@ unitTest(function consoleTable(): void {
 `,
     );
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.table({ 1: { a: 4, b: 5 }, 2: null, 3: { b: 6, c: 7 } }, ["b"]);
     assertEquals(
       stripColor(out.toString()),
@@ -1532,7 +1532,7 @@ unitTest(function consoleTable(): void {
 });
 
 // console.log(Error) test
-unitTest(function consoleLogShouldNotThrowError(): void {
+unitTest(function consoleLogShouldNotThrowError() {
   mockConsole((console) => {
     let result = 0;
     try {
@@ -1545,14 +1545,14 @@ unitTest(function consoleLogShouldNotThrowError(): void {
   });
 
   // output errors to the console should not include "Uncaught"
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.log(new Error("foo"));
     assertEquals(out.toString().includes("Uncaught"), false);
   });
 });
 
 // console.log(Invalid Date) test
-unitTest(function consoleLogShoultNotThrowErrorWhenInvalidDateIsPassed(): void {
+unitTest(function consoleLogShoultNotThrowErrorWhenInvalidDateIsPassed() {
   mockConsole((console, out) => {
     const invalidDate = new Date("test");
     console.log(invalidDate);
@@ -1561,39 +1561,39 @@ unitTest(function consoleLogShoultNotThrowErrorWhenInvalidDateIsPassed(): void {
 });
 
 // console.dir test
-unitTest(function consoleDir(): void {
-  mockConsole((console, out): void => {
+unitTest(function consoleDir() {
+  mockConsole((console, out) => {
     console.dir("DIR");
     assertEquals(out.toString(), "DIR\n");
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.dir("DIR", { indentLevel: 2 });
     assertEquals(out.toString(), "    DIR\n");
   });
 });
 
 // console.dir test
-unitTest(function consoleDirXml(): void {
-  mockConsole((console, out): void => {
+unitTest(function consoleDirXml() {
+  mockConsole((console, out) => {
     console.dirxml("DIRXML");
     assertEquals(out.toString(), "DIRXML\n");
   });
-  mockConsole((console, out): void => {
+  mockConsole((console, out) => {
     console.dirxml("DIRXML", { indentLevel: 2 });
     assertEquals(out.toString(), "    DIRXML\n");
   });
 });
 
 // console.trace test
-unitTest(function consoleTrace(): void {
-  mockConsole((console, _out, err): void => {
+unitTest(function consoleTrace() {
+  mockConsole((console, _out, err) => {
     console.trace("%s", "custom message");
     assert(err);
     assert(err.toString().includes("Trace: custom message"));
   });
 });
 
-unitTest(function inspectString(): void {
+unitTest(function inspectString() {
   assertEquals(
     stripColor(Deno.inspect("\0")),
     `"\\x00"`,
@@ -1604,7 +1604,7 @@ unitTest(function inspectString(): void {
   );
 });
 
-unitTest(function inspectGetters(): void {
+unitTest(function inspectGetters() {
   assertEquals(
     stripColor(Deno.inspect({
       get foo() {
@@ -1633,12 +1633,12 @@ unitTest(function inspectGetters(): void {
   );
 });
 
-unitTest(function inspectPrototype(): void {
+unitTest(function inspectPrototype() {
   class A {}
   assertEquals(Deno.inspect(A.prototype), "A {}");
 });
 
-unitTest(function inspectSorted(): void {
+unitTest(function inspectSorted() {
   assertEquals(
     stripColor(Deno.inspect({ b: 2, a: 1 }, { sorted: true })),
     "{ a: 1, b: 2 }",
@@ -1659,7 +1659,7 @@ unitTest(function inspectSorted(): void {
   );
 });
 
-unitTest(function inspectTrailingComma(): void {
+unitTest(function inspectTrailingComma() {
   assertEquals(
     stripColor(Deno.inspect(
       [
@@ -1714,7 +1714,7 @@ unitTest(function inspectTrailingComma(): void {
   );
 });
 
-unitTest(function inspectCompact(): void {
+unitTest(function inspectCompact() {
   assertEquals(
     stripColor(Deno.inspect({ a: 1, b: 2 }, { compact: false })),
     `{
@@ -1724,7 +1724,7 @@ unitTest(function inspectCompact(): void {
   );
 });
 
-unitTest(function inspectIterableLimit(): void {
+unitTest(function inspectIterableLimit() {
   assertEquals(
     stripColor(Deno.inspect(["a", "b", "c"], { iterableLimit: 2 })),
     `[ "a", "b", ... 1 more items ]`,
@@ -1746,7 +1746,7 @@ unitTest(function inspectIterableLimit(): void {
   );
 });
 
-unitTest(function inspectProxy(): void {
+unitTest(function inspectProxy() {
   assertEquals(
     stripColor(Deno.inspect(
       new Proxy([1, 2, 3], {}),
@@ -1785,7 +1785,7 @@ unitTest(function inspectProxy(): void {
   );
   assertEquals(
     stripColor(Deno.inspect(
-      new Proxy([1, 2, 3], { get(): void {} }),
+      new Proxy([1, 2, 3], { get() {} }),
       { showProxy: true },
     )),
     "Proxy [ [ 1, 2, 3 ], { get: [Function: get] } ]",
@@ -1803,7 +1803,7 @@ unitTest(function inspectProxy(): void {
   );
   assertEquals(
     stripColor(Deno.inspect(
-      new Proxy([1, 2, 3, 4, 5, 6, 7], { get(): void {} }),
+      new Proxy([1, 2, 3, 4, 5, 6, 7], { get() {} }),
       { showProxy: true },
     )),
     `Proxy [ [
@@ -1813,14 +1813,14 @@ unitTest(function inspectProxy(): void {
   );
   assertEquals(
     stripColor(Deno.inspect(
-      new Proxy(function fn() {}, { get(): void {} }),
+      new Proxy(function fn() {}, { get() {} }),
       { showProxy: true },
     )),
     "Proxy [ [Function: fn], { get: [Function: get] } ]",
   );
 });
 
-unitTest(function inspectColors(): void {
+unitTest(function inspectColors() {
   assertEquals(Deno.inspect(1), "1");
   assertStringIncludes(Deno.inspect(1, { colors: true }), "\x1b[");
 });
diff --git a/cli/tests/unit/copy_file_test.ts b/cli/tests/unit/copy_file_test.ts
index 96d08b10e..f89c1c9ee 100644
--- a/cli/tests/unit/copy_file_test.ts
+++ b/cli/tests/unit/copy_file_test.ts
@@ -12,7 +12,7 @@ function readFileString(filename: string | URL): string {
   return dec.decode(dataRead);
 }
 
-function writeFileString(filename: string | URL, s: string): void {
+function writeFileString(filename: string | URL, s: string) {
   const enc = new TextEncoder();
   const data = enc.encode(s);
   Deno.writeFileSync(filename, data, { mode: 0o666 });
@@ -21,7 +21,7 @@ function writeFileString(filename: string | URL, s: string): void {
 function assertSameContent(
   filename1: string | URL,
   filename2: string | URL,
-): void {
+) {
   const data1 = Deno.readFileSync(filename1);
   const data2 = Deno.readFileSync(filename2);
   assertEquals(data1, data2);
@@ -29,7 +29,7 @@ function assertSameContent(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function copyFileSyncSuccess(): void {
+  function copyFileSyncSuccess() {
     const tempDir = Deno.makeTempDirSync();
     const fromFilename = tempDir + "/from.txt";
     const toFilename = tempDir + "/to.txt";
@@ -46,7 +46,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function copyFileSyncByUrl(): void {
+  function copyFileSyncByUrl() {
     const tempDir = Deno.makeTempDirSync();
     const fromUrl = new URL(
       `file://${Deno.build.os === "windows" ? "/" : ""}${tempDir}/from.txt`,
@@ -67,7 +67,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  function copyFileSyncFailure(): void {
+  function copyFileSyncFailure() {
     const tempDir = Deno.makeTempDirSync();
     const fromFilename = tempDir + "/from.txt";
     const toFilename = tempDir + "/to.txt";
@@ -82,7 +82,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: false } },
-  function copyFileSyncPerm1(): void {
+  function copyFileSyncPerm1() {
     assertThrows(() => {
       Deno.copyFileSync("/from.txt", "/to.txt");
     }, Deno.errors.PermissionDenied);
@@ -91,7 +91,7 @@ unitTest(
 
 unitTest(
   { perms: { write: false, read: true } },
-  function copyFileSyncPerm2(): void {
+  function copyFileSyncPerm2() {
     assertThrows(() => {
       Deno.copyFileSync("/from.txt", "/to.txt");
     }, Deno.errors.PermissionDenied);
@@ -100,7 +100,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function copyFileSyncOverwrite(): void {
+  function copyFileSyncOverwrite() {
     const tempDir = Deno.makeTempDirSync();
     const fromFilename = tempDir + "/from.txt";
     const toFilename = tempDir + "/to.txt";
@@ -119,7 +119,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function copyFileSuccess(): Promise<void> {
+  async function copyFileSuccess() {
     const tempDir = Deno.makeTempDirSync();
     const fromFilename = tempDir + "/from.txt";
     const toFilename = tempDir + "/to.txt";
@@ -136,7 +136,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function copyFileByUrl(): Promise<void> {
+  async function copyFileByUrl() {
     const tempDir = Deno.makeTempDirSync();
     const fromUrl = new URL(
       `file://${Deno.build.os === "windows" ? "/" : ""}${tempDir}/from.txt`,
@@ -157,7 +157,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function copyFileFailure(): Promise<void> {
+  async function copyFileFailure() {
     const tempDir = Deno.makeTempDirSync();
     const fromFilename = tempDir + "/from.txt";
     const toFilename = tempDir + "/to.txt";
@@ -172,7 +172,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function copyFileOverwrite(): Promise<void> {
+  async function copyFileOverwrite() {
     const tempDir = Deno.makeTempDirSync();
     const fromFilename = tempDir + "/from.txt";
     const toFilename = tempDir + "/to.txt";
@@ -191,7 +191,7 @@ unitTest(
 
 unitTest(
   { perms: { read: false, write: true } },
-  async function copyFilePerm1(): Promise<void> {
+  async function copyFilePerm1() {
     await assertThrowsAsync(async () => {
       await Deno.copyFile("/from.txt", "/to.txt");
     }, Deno.errors.PermissionDenied);
@@ -200,7 +200,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: false } },
-  async function copyFilePerm2(): Promise<void> {
+  async function copyFilePerm2() {
     await assertThrowsAsync(async () => {
       await Deno.copyFile("/from.txt", "/to.txt");
     }, Deno.errors.PermissionDenied);
diff --git a/cli/tests/unit/custom_event_test.ts b/cli/tests/unit/custom_event_test.ts
index 0db770056..3b6242996 100644
--- a/cli/tests/unit/custom_event_test.ts
+++ b/cli/tests/unit/custom_event_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertEquals, unitTest } from "./test_util.ts";
 
-unitTest(function customEventInitializedWithDetail(): void {
+unitTest(function customEventInitializedWithDetail() {
   const type = "touchstart";
   const detail = { message: "hello" };
   const customEventInit = {
@@ -20,7 +20,7 @@ unitTest(function customEventInitializedWithDetail(): void {
   assertEquals(event.type, type);
 });
 
-unitTest(function toStringShouldBeWebCompatibility(): void {
+unitTest(function toStringShouldBeWebCompatibility() {
   const type = "touchstart";
   const event = new CustomEvent(type, {});
   assertEquals(event.toString(), "[object CustomEvent]");
diff --git a/cli/tests/unit/dir_test.ts b/cli/tests/unit/dir_test.ts
index e64baf97b..baed6f6d6 100644
--- a/cli/tests/unit/dir_test.ts
+++ b/cli/tests/unit/dir_test.ts
@@ -1,13 +1,13 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, assertEquals, assertThrows, unitTest } from "./test_util.ts";
 
-unitTest({ perms: { read: true } }, function dirCwdNotNull(): void {
+unitTest({ perms: { read: true } }, function dirCwdNotNull() {
   assert(Deno.cwd() != null);
 });
 
 unitTest(
   { perms: { read: true, write: true } },
-  function dirCwdChdirSuccess(): void {
+  function dirCwdChdirSuccess() {
     const initialdir = Deno.cwd();
     const path = Deno.makeTempDirSync();
     Deno.chdir(path);
@@ -21,7 +21,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: true, write: true } }, function dirCwdError(): void {
+unitTest({ perms: { read: true, write: true } }, function dirCwdError() {
   // excluding windows since it throws resource busy, while removeSync
   if (["linux", "darwin"].includes(Deno.build.os)) {
     const initialdir = Deno.cwd();
@@ -38,7 +38,7 @@ unitTest({ perms: { read: true, write: true } }, function dirCwdError(): void {
   }
 });
 
-unitTest({ perms: { read: false } }, function dirCwdPermError(): void {
+unitTest({ perms: { read: false } }, function dirCwdPermError() {
   assertThrows(
     () => {
       Deno.cwd();
@@ -50,7 +50,7 @@ unitTest({ perms: { read: false } }, function dirCwdPermError(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function dirChdirError(): void {
+  function dirChdirError() {
     const path = Deno.makeTempDirSync() + "test";
     assertThrows(() => {
       Deno.chdir(path);
diff --git a/cli/tests/unit/dom_exception_test.ts b/cli/tests/unit/dom_exception_test.ts
index ea310fc9a..b5f5b1f87 100644
--- a/cli/tests/unit/dom_exception_test.ts
+++ b/cli/tests/unit/dom_exception_test.ts
@@ -1,6 +1,6 @@
 import { assertEquals, assertStringIncludes, unitTest } from "./test_util.ts";
 
-unitTest(function customInspectFunction(): void {
+unitTest(function customInspectFunction() {
   const blob = new DOMException("test");
   assertEquals(
     Deno.inspect(blob),
diff --git a/cli/tests/unit/error_stack_test.ts b/cli/tests/unit/error_stack_test.ts
index 1445124e9..0da3ff993 100644
--- a/cli/tests/unit/error_stack_test.ts
+++ b/cli/tests/unit/error_stack_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, assertEquals, assertMatch, unitTest } from "./test_util.ts";
 
-unitTest(function errorStackMessageLine(): void {
+unitTest(function errorStackMessageLine() {
   const e1 = new Error();
   e1.name = "Foo";
   e1.message = "bar";
@@ -41,8 +41,8 @@ unitTest(function errorStackMessageLine(): void {
   assertMatch(e6.stack!, /^null: null\n/);
 });
 
-unitTest(function captureStackTrace(): void {
-  function foo(): void {
+unitTest(function captureStackTrace() {
+  function foo() {
     const error = new Error();
     const stack1 = error.stack!;
     Error.captureStackTrace(error, foo);
@@ -55,7 +55,7 @@ unitTest(function captureStackTrace(): void {
 
 // FIXME(bartlomieju): no longer works after migrating
 // to JavaScript runtime code
-unitTest({ ignore: true }, function applySourceMap(): void {
+unitTest({ ignore: true }, function applySourceMap() {
   const result = Deno.applySourceMap({
     fileName: "CLI_SNAPSHOT.js",
     lineNumber: 23,
diff --git a/cli/tests/unit/event_target_test.ts b/cli/tests/unit/event_target_test.ts
index 29de04c8c..0d0d89154 100644
--- a/cli/tests/unit/event_target_test.ts
+++ b/cli/tests/unit/event_target_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertEquals, unitTest } from "./test_util.ts";
 
-unitTest(function addEventListenerTest(): void {
+unitTest(function addEventListenerTest() {
   const document = new EventTarget();
 
   assertEquals(document.addEventListener("x", null, false), undefined);
@@ -9,12 +9,12 @@ unitTest(function addEventListenerTest(): void {
   assertEquals(document.addEventListener("x", null), undefined);
 });
 
-unitTest(function constructedEventTargetCanBeUsedAsExpected(): void {
+unitTest(function constructedEventTargetCanBeUsedAsExpected() {
   const target = new EventTarget();
   const event = new Event("foo", { bubbles: true, cancelable: false });
   let callCount = 0;
 
-  const listener = (e: Event): void => {
+  const listener = (e: Event) => {
     assertEquals(e, event);
     ++callCount;
   };
@@ -32,13 +32,13 @@ unitTest(function constructedEventTargetCanBeUsedAsExpected(): void {
   assertEquals(callCount, 2);
 });
 
-unitTest(function anEventTargetCanBeSubclassed(): void {
+unitTest(function anEventTargetCanBeSubclassed() {
   class NicerEventTarget extends EventTarget {
     on(
       type: string,
       callback: ((e: Event) => void) | null,
       options?: AddEventListenerOptions,
-    ): void {
+    ) {
       this.addEventListener(type, callback, options);
     }
 
@@ -46,7 +46,7 @@ unitTest(function anEventTargetCanBeSubclassed(): void {
       type: string,
       callback: ((e: Event) => void) | null,
       options?: EventListenerOptions,
-    ): void {
+    ) {
       this.removeEventListener(type, callback, options);
     }
   }
@@ -55,7 +55,7 @@ unitTest(function anEventTargetCanBeSubclassed(): void {
   new Event("foo", { bubbles: true, cancelable: false });
   let callCount = 0;
 
-  const listener = (): void => {
+  const listener = () => {
     ++callCount;
   };
 
@@ -66,19 +66,19 @@ unitTest(function anEventTargetCanBeSubclassed(): void {
   assertEquals(callCount, 0);
 });
 
-unitTest(function removingNullEventListenerShouldSucceed(): void {
+unitTest(function removingNullEventListenerShouldSucceed() {
   const document = new EventTarget();
   assertEquals(document.removeEventListener("x", null, false), undefined);
   assertEquals(document.removeEventListener("x", null, true), undefined);
   assertEquals(document.removeEventListener("x", null), undefined);
 });
 
-unitTest(function constructedEventTargetUseObjectPrototype(): void {
+unitTest(function constructedEventTargetUseObjectPrototype() {
   const target = new EventTarget();
   const event = new Event("toString", { bubbles: true, cancelable: false });
   let callCount = 0;
 
-  const listener = (e: Event): void => {
+  const listener = (e: Event) => {
     assertEquals(e, event);
     ++callCount;
   };
@@ -96,12 +96,12 @@ unitTest(function constructedEventTargetUseObjectPrototype(): void {
   assertEquals(callCount, 2);
 });
 
-unitTest(function toStringShouldBeWebCompatible(): void {
+unitTest(function toStringShouldBeWebCompatible() {
   const target = new EventTarget();
   assertEquals(target.toString(), "[object EventTarget]");
 });
 
-unitTest(function dispatchEventShouldNotThrowError(): void {
+unitTest(function dispatchEventShouldNotThrowError() {
   let hasThrown = false;
 
   try {
@@ -110,7 +110,7 @@ unitTest(function dispatchEventShouldNotThrowError(): void {
       bubbles: true,
       cancelable: false,
     });
-    const listener = (): void => {};
+    const listener = () => {};
     target.addEventListener("hasOwnProperty", listener);
     target.dispatchEvent(event);
   } catch {
@@ -120,7 +120,7 @@ unitTest(function dispatchEventShouldNotThrowError(): void {
   assertEquals(hasThrown, false);
 });
 
-unitTest(function eventTargetThisShouldDefaultToWindow(): void {
+unitTest(function eventTargetThisShouldDefaultToWindow() {
   const {
     addEventListener,
     dispatchEvent,
@@ -128,7 +128,7 @@ unitTest(function eventTargetThisShouldDefaultToWindow(): void {
   } = EventTarget.prototype;
   let n = 1;
   const event = new Event("hello");
-  const listener = (): void => {
+  const listener = () => {
     n = 2;
   };
 
@@ -149,13 +149,13 @@ unitTest(function eventTargetThisShouldDefaultToWindow(): void {
   assertEquals(n, 1);
 });
 
-unitTest(function eventTargetShouldAcceptEventListenerObject(): void {
+unitTest(function eventTargetShouldAcceptEventListenerObject() {
   const target = new EventTarget();
   const event = new Event("foo", { bubbles: true, cancelable: false });
   let callCount = 0;
 
   const listener = {
-    handleEvent(e: Event): void {
+    handleEvent(e: Event) {
       assertEquals(e, event);
       ++callCount;
     },
@@ -174,12 +174,12 @@ unitTest(function eventTargetShouldAcceptEventListenerObject(): void {
   assertEquals(callCount, 2);
 });
 
-unitTest(function eventTargetShouldAcceptAsyncFunction(): void {
+unitTest(function eventTargetShouldAcceptAsyncFunction() {
   const target = new EventTarget();
   const event = new Event("foo", { bubbles: true, cancelable: false });
   let callCount = 0;
 
-  const listener = (e: Event): void => {
+  const listener = (e: Event) => {
     assertEquals(e, event);
     ++callCount;
   };
@@ -198,13 +198,13 @@ unitTest(function eventTargetShouldAcceptAsyncFunction(): void {
 });
 
 unitTest(
-  function eventTargetShouldAcceptAsyncFunctionForEventListenerObject(): void {
+  function eventTargetShouldAcceptAsyncFunctionForEventListenerObject() {
     const target = new EventTarget();
     const event = new Event("foo", { bubbles: true, cancelable: false });
     let callCount = 0;
 
     const listener = {
-      handleEvent(e: Event): void {
+      handleEvent(e: Event) {
         assertEquals(e, event);
         ++callCount;
       },
@@ -223,7 +223,7 @@ unitTest(
     assertEquals(callCount, 2);
   },
 );
-unitTest(function eventTargetDispatchShouldSetTargetNoListener(): void {
+unitTest(function eventTargetDispatchShouldSetTargetNoListener() {
   const target = new EventTarget();
   const event = new Event("foo");
   assertEquals(event.target, null);
@@ -231,7 +231,7 @@ unitTest(function eventTargetDispatchShouldSetTargetNoListener(): void {
   assertEquals(event.target, target);
 });
 
-unitTest(function eventTargetDispatchShouldSetTargetInListener(): void {
+unitTest(function eventTargetDispatchShouldSetTargetInListener() {
   const target = new EventTarget();
   const event = new Event("foo");
   assertEquals(event.target, null);
diff --git a/cli/tests/unit/event_test.ts b/cli/tests/unit/event_test.ts
index c7cd2f58d..13f2590ce 100644
--- a/cli/tests/unit/event_test.ts
+++ b/cli/tests/unit/event_test.ts
@@ -6,7 +6,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest(function eventInitializedWithType(): void {
+unitTest(function eventInitializedWithType() {
   const type = "click";
   const event = new Event(type);
 
@@ -18,7 +18,7 @@ unitTest(function eventInitializedWithType(): void {
   assertEquals(event.cancelable, false);
 });
 
-unitTest(function eventInitializedWithTypeAndDict(): void {
+unitTest(function eventInitializedWithTypeAndDict() {
   const init = "submit";
   const eventInit = { bubbles: true, cancelable: true } as EventInit;
   const event = new Event(init, eventInit);
@@ -31,7 +31,7 @@ unitTest(function eventInitializedWithTypeAndDict(): void {
   assertEquals(event.cancelable, true);
 });
 
-unitTest(function eventComposedPathSuccess(): void {
+unitTest(function eventComposedPathSuccess() {
   const type = "click";
   const event = new Event(type);
   const composedPath = event.composedPath();
@@ -39,7 +39,7 @@ unitTest(function eventComposedPathSuccess(): void {
   assertEquals(composedPath, []);
 });
 
-unitTest(function eventStopPropagationSuccess(): void {
+unitTest(function eventStopPropagationSuccess() {
   const type = "click";
   const event = new Event(type);
 
@@ -48,7 +48,7 @@ unitTest(function eventStopPropagationSuccess(): void {
   assertEquals(event.cancelBubble, true);
 });
 
-unitTest(function eventStopImmediatePropagationSuccess(): void {
+unitTest(function eventStopImmediatePropagationSuccess() {
   const type = "click";
   const event = new Event(type);
 
@@ -57,7 +57,7 @@ unitTest(function eventStopImmediatePropagationSuccess(): void {
   assertEquals(event.cancelBubble, true);
 });
 
-unitTest(function eventPreventDefaultSuccess(): void {
+unitTest(function eventPreventDefaultSuccess() {
   const type = "click";
   const event = new Event(type);
 
@@ -72,7 +72,7 @@ unitTest(function eventPreventDefaultSuccess(): void {
   assertEquals(cancelableEvent.defaultPrevented, true);
 });
 
-unitTest(function eventInitializedWithNonStringType(): void {
+unitTest(function eventInitializedWithNonStringType() {
   // deno-lint-ignore no-explicit-any
   const type: any = undefined;
   const event = new Event(type);
@@ -86,7 +86,7 @@ unitTest(function eventInitializedWithNonStringType(): void {
 });
 
 // ref https://github.com/web-platform-tests/wpt/blob/master/dom/events/Event-isTrusted.any.js
-unitTest(function eventIsTrusted(): void {
+unitTest(function eventIsTrusted() {
   const desc1 = Object.getOwnPropertyDescriptor(new Event("x"), "isTrusted");
   assert(desc1);
   assertEquals(typeof desc1.get, "function");
@@ -98,7 +98,7 @@ unitTest(function eventIsTrusted(): void {
   assertEquals(desc1!.get, desc2!.get);
 });
 
-unitTest(function eventInspectOutput(): void {
+unitTest(function eventInspectOutput() {
   // deno-lint-ignore no-explicit-any
   const cases: Array<[any, (event: any) => string]> = [
     [
@@ -133,7 +133,7 @@ unitTest(function eventInspectOutput(): void {
   }
 });
 
-unitTest(function inspectEvent(): void {
+unitTest(function inspectEvent() {
   // has a customInspect implementation that previously would throw on a getter
   assertEquals(
     Deno.inspect(Event.prototype),
diff --git a/cli/tests/unit/fetch_test.ts b/cli/tests/unit/fetch_test.ts
index 45ab2d12c..24825c653 100644
--- a/cli/tests/unit/fetch_test.ts
+++ b/cli/tests/unit/fetch_test.ts
@@ -12,7 +12,7 @@ import { Buffer } from "../../../test_util/std/io/buffer.ts";
 
 unitTest(
   { perms: { net: true } },
-  async function fetchRequiresOneArgument(): Promise<void> {
+  async function fetchRequiresOneArgument() {
     await assertThrowsAsync(
       fetch as unknown as () => Promise<void>,
       TypeError,
@@ -20,11 +20,9 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function fetchProtocolError(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchProtocolError() {
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await fetch("file:///");
     },
     TypeError,
@@ -58,10 +56,10 @@ function findClosedPortInRange(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchConnectionError(): Promise<void> {
+  async function fetchConnectionError() {
     const port = findClosedPortInRange(4000, 9999);
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         await fetch(`http://localhost:${port}`);
       },
       TypeError,
@@ -72,9 +70,9 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchDnsError(): Promise<void> {
+  async function fetchDnsError() {
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         await fetch("http://nil/");
       },
       TypeError,
@@ -85,9 +83,9 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInvalidUriError(): Promise<void> {
+  async function fetchInvalidUriError() {
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         await fetch("http://<invalid>/");
       },
       TypeError,
@@ -95,27 +93,25 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function fetchJsonSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchJsonSuccess() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   const json = await response.json();
   assertEquals(json.name, "deno");
 });
 
-unitTest(async function fetchPerm(): Promise<void> {
+unitTest(async function fetchPerm() {
   await assertThrowsAsync(async () => {
     await fetch("http://localhost:4545/cli/tests/fixture.json");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { net: true } }, async function fetchUrl(): Promise<void> {
+unitTest({ perms: { net: true } }, async function fetchUrl() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   assertEquals(response.url, "http://localhost:4545/cli/tests/fixture.json");
   const _json = await response.json();
 });
 
-unitTest({ perms: { net: true } }, async function fetchURL(): Promise<void> {
+unitTest({ perms: { net: true } }, async function fetchURL() {
   const response = await fetch(
     new URL("http://localhost:4545/cli/tests/fixture.json"),
   );
@@ -123,16 +119,14 @@ unitTest({ perms: { net: true } }, async function fetchURL(): Promise<void> {
   const _json = await response.json();
 });
 
-unitTest({ perms: { net: true } }, async function fetchHeaders(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchHeaders() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   const headers = response.headers;
   assertEquals(headers.get("Content-Type"), "application/json");
   const _json = await response.json();
 });
 
-unitTest({ perms: { net: true } }, async function fetchBlob(): Promise<void> {
+unitTest({ perms: { net: true } }, async function fetchBlob() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   const headers = response.headers;
   const blob = await response.blob();
@@ -142,7 +136,7 @@ unitTest({ perms: { net: true } }, async function fetchBlob(): Promise<void> {
 
 unitTest(
   { perms: { net: true } },
-  async function fetchBodyUsedReader(): Promise<void> {
+  async function fetchBodyUsedReader() {
     const response = await fetch(
       "http://localhost:4545/cli/tests/fixture.json",
     );
@@ -160,7 +154,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchBodyUsedCancelStream(): Promise<void> {
+  async function fetchBodyUsedCancelStream() {
     const response = await fetch(
       "http://localhost:4545/cli/tests/fixture.json",
     );
@@ -173,9 +167,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function fetchAsyncIterator(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchAsyncIterator() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   const headers = response.headers;
 
@@ -189,9 +181,7 @@ unitTest({ perms: { net: true } }, async function fetchAsyncIterator(): Promise<
   assertEquals(total, Number(headers.get("Content-Length")));
 });
 
-unitTest({ perms: { net: true } }, async function fetchBodyReader(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchBodyReader() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   const headers = response.headers;
   assert(response.body !== null);
@@ -210,7 +200,7 @@ unitTest({ perms: { net: true } }, async function fetchBodyReader(): Promise<
 
 unitTest(
   { perms: { net: true } },
-  async function fetchBodyReaderBigBody(): Promise<void> {
+  async function fetchBodyReaderBigBody() {
     const data = "a".repeat(10 << 10); // 10mb
     const response = await fetch("http://localhost:4545/echo_server", {
       method: "POST",
@@ -230,9 +220,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function responseClone(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function responseClone() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
   const response1 = response.clone();
   assert(response !== response1);
@@ -247,7 +235,7 @@ unitTest({ perms: { net: true } }, async function responseClone(): Promise<
 
 unitTest(
   { perms: { net: true } },
-  async function fetchMultipartFormDataSuccess(): Promise<void> {
+  async function fetchMultipartFormDataSuccess() {
     const response = await fetch(
       "http://localhost:4545/multipart_form_data.txt",
     );
@@ -264,14 +252,14 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchMultipartFormBadContentType(): Promise<void> {
+  async function fetchMultipartFormBadContentType() {
     const response = await fetch(
       "http://localhost:4545/multipart_form_bad_content_type",
     );
     assert(response.body !== null);
 
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         await response.formData();
       },
       TypeError,
@@ -282,7 +270,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchURLEncodedFormDataSuccess(): Promise<void> {
+  async function fetchURLEncodedFormDataSuccess() {
     const response = await fetch(
       "http://localhost:4545/cli/tests/subdir/form_urlencoded.txt",
     );
@@ -296,7 +284,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitFormDataBinaryFileBody(): Promise<void> {
+  async function fetchInitFormDataBinaryFileBody() {
     // Some random bytes
     // deno-fmt-ignore
     const binaryFile = new Uint8Array([108,2,0,0,145,22,162,61,157,227,166,77,138,75,180,56,119,188,177,183]);
@@ -315,7 +303,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitFormDataMultipleFilesBody(): Promise<void> {
+  async function fetchInitFormDataMultipleFilesBody() {
     const files = [
       {
         // deno-fmt-ignore
@@ -371,7 +359,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithRedirection(): Promise<void> {
+  async function fetchWithRedirection() {
     const response = await fetch("http://localhost:4546/README.md");
     assertEquals(response.status, 200);
     assertEquals(response.statusText, "OK");
@@ -385,7 +373,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithRelativeRedirection(): Promise<void> {
+  async function fetchWithRelativeRedirection() {
     const response = await fetch(
       "http://localhost:4545/cli/tests/001_hello.js",
     );
@@ -400,7 +388,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithRelativeRedirectionUrl(): Promise<void> {
+  async function fetchWithRelativeRedirectionUrl() {
     const cases = [
       ["end", "http://localhost:4550/a/b/end"],
       ["/end", "http://localhost:4550/end"],
@@ -421,7 +409,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithInfRedirection(): Promise<void> {
+  async function fetchWithInfRedirection() {
     await assertThrowsAsync(
       () => fetch("http://localhost:4549/cli/tests"),
       TypeError,
@@ -432,7 +420,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitStringBody(): Promise<void> {
+  async function fetchInitStringBody() {
     const data = "Hello World";
     const response = await fetch("http://localhost:4545/echo_server", {
       method: "POST",
@@ -446,7 +434,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchRequestInitStringBody(): Promise<void> {
+  async function fetchRequestInitStringBody() {
     const data = "Hello World";
     const req = new Request("http://localhost:4545/echo_server", {
       method: "POST",
@@ -460,7 +448,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchSeparateInit(): Promise<void> {
+  async function fetchSeparateInit() {
     // related to: https://github.com/denoland/deno/issues/10396
     const req = new Request("http://localhost:4545/cli/tests/001_hello.js");
     const init = {
@@ -475,7 +463,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitTypedArrayBody(): Promise<void> {
+  async function fetchInitTypedArrayBody() {
     const data = "Hello World";
     const response = await fetch("http://localhost:4545/echo_server", {
       method: "POST",
@@ -488,7 +476,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitArrayBufferBody(): Promise<void> {
+  async function fetchInitArrayBufferBody() {
     const data = "Hello World";
     const response = await fetch("http://localhost:4545/echo_server", {
       method: "POST",
@@ -501,7 +489,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitURLSearchParamsBody(): Promise<void> {
+  async function fetchInitURLSearchParamsBody() {
     const data = "param1=value1&param2=value2";
     const params = new URLSearchParams(data);
     const response = await fetch("http://localhost:4545/echo_server", {
@@ -518,9 +506,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function fetchInitBlobBody(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchInitBlobBody() {
   const data = "const a = 1";
   const blob = new Blob([data], {
     type: "text/javascript",
@@ -536,7 +522,7 @@ unitTest({ perms: { net: true } }, async function fetchInitBlobBody(): Promise<
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitFormDataBody(): Promise<void> {
+  async function fetchInitFormDataBody() {
     const form = new FormData();
     form.append("field", "value");
     const response = await fetch("http://localhost:4545/echo_server", {
@@ -550,7 +536,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitFormDataBlobFilenameBody(): Promise<void> {
+  async function fetchInitFormDataBlobFilenameBody() {
     const form = new FormData();
     form.append("field", "value");
     form.append("file", new Blob([new TextEncoder().encode("deno")]));
@@ -568,7 +554,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchInitFormDataTextFileBody(): Promise<void> {
+  async function fetchInitFormDataTextFileBody() {
     const fileContent = "deno land";
     const form = new FormData();
     form.append("field", "value");
@@ -596,9 +582,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function fetchUserAgent(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchUserAgent() {
   const data = "Hello World";
   const response = await fetch("http://localhost:4545/echo_server", {
     method: "POST",
@@ -658,7 +642,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchRequest(): Promise<void> {
+  async function fetchRequest() {
     const addr = "127.0.0.1:4501";
     const buf = bufferServer(addr);
     const response = await fetch(`http://${addr}/blah`, {
@@ -690,7 +674,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchPostBodyString(): Promise<void> {
+  async function fetchPostBodyString() {
     const addr = "127.0.0.1:4502";
     const buf = bufferServer(addr);
     const body = "hello world";
@@ -727,7 +711,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchPostBodyTypedArray(): Promise<void> {
+  async function fetchPostBodyTypedArray() {
     const addr = "127.0.0.1:4503";
     const buf = bufferServer(addr);
     const bodyStr = "hello world";
@@ -764,7 +748,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithNonAsciiRedirection(): Promise<void> {
+  async function fetchWithNonAsciiRedirection() {
     const response = await fetch("http://localhost:4545/non_ascii_redirect", {
       redirect: "manual",
     });
@@ -778,7 +762,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithManualRedirection(): Promise<void> {
+  async function fetchWithManualRedirection() {
     const response = await fetch("http://localhost:4546/", {
       redirect: "manual",
     }); // will redirect to http://localhost:4545/
@@ -794,7 +778,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchWithErrorRedirection(): Promise<void> {
+  async function fetchWithErrorRedirection() {
     await assertThrowsAsync(
       () =>
         fetch("http://localhost:4546/", {
@@ -806,7 +790,7 @@ unitTest(
   },
 );
 
-unitTest(function responseRedirect(): void {
+unitTest(function responseRedirect() {
   const redir = Response.redirect("example.com/newLocation", 301);
   assertEquals(redir.status, 301);
   assertEquals(redir.statusText, "");
@@ -818,7 +802,7 @@ unitTest(function responseRedirect(): void {
   assertEquals(redir.type, "default");
 });
 
-unitTest(async function responseWithoutBody(): Promise<void> {
+unitTest(async function responseWithoutBody() {
   const response = new Response();
   assertEquals(await response.arrayBuffer(), new ArrayBuffer(0));
   const blob = await response.blob();
@@ -830,9 +814,7 @@ unitTest(async function responseWithoutBody(): Promise<void> {
   });
 });
 
-unitTest({ perms: { net: true } }, async function fetchBodyReadTwice(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function fetchBodyReadTwice() {
   const response = await fetch("http://localhost:4545/cli/tests/fixture.json");
 
   // Read body
@@ -855,7 +837,7 @@ unitTest({ perms: { net: true } }, async function fetchBodyReadTwice(): Promise<
 
 unitTest(
   { perms: { net: true } },
-  async function fetchBodyReaderAfterRead(): Promise<void> {
+  async function fetchBodyReaderAfterRead() {
     const response = await fetch(
       "http://localhost:4545/cli/tests/fixture.json",
     );
@@ -878,7 +860,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchBodyReaderWithCancelAndNewReader(): Promise<void> {
+  async function fetchBodyReaderWithCancelAndNewReader() {
     const data = "a".repeat(1 << 10);
     const response = await fetch("http://localhost:4545/echo_server", {
       method: "POST",
@@ -906,7 +888,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchBodyReaderWithReadCancelAndNewReader(): Promise<void> {
+  async function fetchBodyReaderWithReadCancelAndNewReader() {
     const data = "a".repeat(1 << 10);
 
     const response = await fetch("http://localhost:4545/echo_server", {
@@ -936,7 +918,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchResourceCloseAfterStreamCancel(): Promise<void> {
+  async function fetchResourceCloseAfterStreamCancel() {
     const res = await fetch("http://localhost:4545/cli/tests/fixture.json");
     assert(res.body !== null);
 
@@ -954,7 +936,7 @@ unitTest(
 // the software in your host machine. (os error 10053)
 unitTest(
   { perms: { net: true }, ignore: Deno.build.os == "windows" },
-  async function fetchNullBodyStatus(): Promise<void> {
+  async function fetchNullBodyStatus() {
     const nullBodyStatus = [101, 204, 205, 304];
 
     for (const status of nullBodyStatus) {
@@ -972,7 +954,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function fetchResponseContentLength(): Promise<void> {
+  async function fetchResponseContentLength() {
     const body = new Uint8Array(2 ** 16);
     const headers = new Headers([["content-type", "application/octet-stream"]]);
     const res = await fetch("http://localhost:4545/echo_server", {
@@ -989,7 +971,7 @@ unitTest(
   },
 );
 
-unitTest(function fetchResponseConstructorNullBody(): void {
+unitTest(function fetchResponseConstructorNullBody() {
   const nullBodyStatus = [204, 205, 304];
 
   for (const status of nullBodyStatus) {
@@ -1006,7 +988,7 @@ unitTest(function fetchResponseConstructorNullBody(): void {
   }
 });
 
-unitTest(function fetchResponseConstructorInvalidStatus(): void {
+unitTest(function fetchResponseConstructorInvalidStatus() {
   const invalidStatus = [101, 600, 199, null, "", NaN];
 
   for (const status of invalidStatus) {
@@ -1022,7 +1004,7 @@ unitTest(function fetchResponseConstructorInvalidStatus(): void {
   }
 });
 
-unitTest(function fetchResponseEmptyConstructor(): void {
+unitTest(function fetchResponseEmptyConstructor() {
   const response = new Response();
   assertEquals(response.status, 200);
   assertEquals(response.body, null);
@@ -1099,7 +1081,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function fetchPostBodyReadableStream(): Promise<void> {
+  async function fetchPostBodyReadableStream() {
     const addr = "127.0.0.1:4502";
     const buf = bufferServer(addr);
     const stream = new TransformStream();
@@ -1143,7 +1125,7 @@ unitTest(
   },
 );
 
-unitTest({}, function fetchWritableRespProps(): void {
+unitTest({}, function fetchWritableRespProps() {
   const original = new Response("https://deno.land", {
     status: 404,
     headers: { "x-deno": "foo" },
diff --git a/cli/tests/unit/file_test.ts b/cli/tests/unit/file_test.ts
index f4bb0bb4d..52dd1365e 100644
--- a/cli/tests/unit/file_test.ts
+++ b/cli/tests/unit/file_test.ts
@@ -2,7 +2,7 @@
 import { assert, assertEquals, unitTest } from "./test_util.ts";
 
 // deno-lint-ignore no-explicit-any
-function testFirstArgument(arg1: any[], expectedSize: number): void {
+function testFirstArgument(arg1: any[], expectedSize: number) {
   const file = new File(arg1, "name");
   assert(file instanceof File);
   assertEquals(file.name, "name");
@@ -10,47 +10,47 @@ function testFirstArgument(arg1: any[], expectedSize: number): void {
   assertEquals(file.type, "");
 }
 
-unitTest(function fileEmptyFileBits(): void {
+unitTest(function fileEmptyFileBits() {
   testFirstArgument([], 0);
 });
 
-unitTest(function fileStringFileBits(): void {
+unitTest(function fileStringFileBits() {
   testFirstArgument(["bits"], 4);
 });
 
-unitTest(function fileUnicodeStringFileBits(): void {
+unitTest(function fileUnicodeStringFileBits() {
   testFirstArgument(["𝓽𝓮𝔁𝓽"], 16);
 });
 
-unitTest(function fileStringObjectFileBits(): void {
+unitTest(function fileStringObjectFileBits() {
   testFirstArgument([new String("string object")], 13);
 });
 
-unitTest(function fileEmptyBlobFileBits(): void {
+unitTest(function fileEmptyBlobFileBits() {
   testFirstArgument([new Blob()], 0);
 });
 
-unitTest(function fileBlobFileBits(): void {
+unitTest(function fileBlobFileBits() {
   testFirstArgument([new Blob(["bits"])], 4);
 });
 
-unitTest(function fileEmptyFileFileBits(): void {
+unitTest(function fileEmptyFileFileBits() {
   testFirstArgument([new File([], "world.txt")], 0);
 });
 
-unitTest(function fileFileFileBits(): void {
+unitTest(function fileFileFileBits() {
   testFirstArgument([new File(["bits"], "world.txt")], 4);
 });
 
-unitTest(function fileArrayBufferFileBits(): void {
+unitTest(function fileArrayBufferFileBits() {
   testFirstArgument([new ArrayBuffer(8)], 8);
 });
 
-unitTest(function fileTypedArrayFileBits(): void {
+unitTest(function fileTypedArrayFileBits() {
   testFirstArgument([new Uint8Array([0x50, 0x41, 0x53, 0x53])], 4);
 });
 
-unitTest(function fileVariousFileBits(): void {
+unitTest(function fileVariousFileBits() {
   testFirstArgument(
     [
       "bits",
@@ -64,45 +64,45 @@ unitTest(function fileVariousFileBits(): void {
   );
 });
 
-unitTest(function fileNumberInFileBits(): void {
+unitTest(function fileNumberInFileBits() {
   testFirstArgument([12], 2);
 });
 
-unitTest(function fileArrayInFileBits(): void {
+unitTest(function fileArrayInFileBits() {
   testFirstArgument([[1, 2, 3]], 5);
 });
 
-unitTest(function fileObjectInFileBits(): void {
+unitTest(function fileObjectInFileBits() {
   // "[object Object]"
   testFirstArgument([{}], 15);
 });
 
 // deno-lint-ignore no-explicit-any
-function testSecondArgument(arg2: any, expectedFileName: string): void {
+function testSecondArgument(arg2: any, expectedFileName: string) {
   const file = new File(["bits"], arg2);
   assert(file instanceof File);
   assertEquals(file.name, expectedFileName);
 }
 
-unitTest(function fileUsingFileName(): void {
+unitTest(function fileUsingFileName() {
   testSecondArgument("dummy", "dummy");
 });
 
-unitTest(function fileUsingNullFileName(): void {
+unitTest(function fileUsingNullFileName() {
   testSecondArgument(null, "null");
 });
 
-unitTest(function fileUsingNumberFileName(): void {
+unitTest(function fileUsingNumberFileName() {
   testSecondArgument(1, "1");
 });
 
-unitTest(function fileUsingEmptyStringFileName(): void {
+unitTest(function fileUsingEmptyStringFileName() {
   testSecondArgument("", "");
 });
 
 unitTest(
   { perms: { read: true, write: true } },
-  function fileTruncateSyncSuccess(): void {
+  function fileTruncateSyncSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_fileTruncateSync.txt";
     const file = Deno.openSync(filename, {
       create: true,
@@ -124,7 +124,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function fileTruncateSuccess(): Promise<void> {
+  async function fileTruncateSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_fileTruncate.txt";
     const file = await Deno.open(filename, {
       create: true,
@@ -144,7 +144,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: true } }, function fileStatSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function fileStatSyncSuccess() {
   const file = Deno.openSync("README.md");
   const fileInfo = file.statSync();
   assert(fileInfo.isFile);
@@ -159,9 +159,7 @@ unitTest({ perms: { read: true } }, function fileStatSyncSuccess(): void {
   file.close();
 });
 
-unitTest({ perms: { read: true } }, async function fileStatSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function fileStatSuccess() {
   const file = await Deno.open("README.md");
   const fileInfo = await file.stat();
   assert(fileInfo.isFile);
diff --git a/cli/tests/unit/filereader_test.ts b/cli/tests/unit/filereader_test.ts
index eb1f11475..bc9beab70 100644
--- a/cli/tests/unit/filereader_test.ts
+++ b/cli/tests/unit/filereader_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertEquals, unitTest } from "./test_util.ts";
 
-unitTest(function fileReaderConstruct(): void {
+unitTest(function fileReaderConstruct() {
   const fr = new FileReader();
   assertEquals(fr.readyState, FileReader.EMPTY);
 
@@ -10,7 +10,7 @@ unitTest(function fileReaderConstruct(): void {
   assertEquals(FileReader.DONE, 2);
 });
 
-unitTest(async function fileReaderLoadBlob(): Promise<void> {
+unitTest(async function fileReaderLoadBlob() {
   await new Promise<void>((resolve) => {
     const fr = new FileReader();
     const b1 = new Blob(["Hello World"]);
@@ -44,18 +44,18 @@ unitTest(async function fileReaderLoadBlob(): Promise<void> {
       hasDispatchedEvents.progress += 1;
     });
 
-    fr.onloadstart = (): void => {
+    fr.onloadstart = () => {
       hasOnEvents.loadstart = true;
     };
-    fr.onprogress = (): void => {
+    fr.onprogress = () => {
       assertEquals(fr.readyState, FileReader.LOADING);
 
       hasOnEvents.progress += 1;
     };
-    fr.onload = (): void => {
+    fr.onload = () => {
       hasOnEvents.load = true;
     };
-    fr.onloadend = (ev): void => {
+    fr.onloadend = (ev) => {
       hasOnEvents.loadend = true;
       result = fr.result as string;
 
@@ -77,7 +77,7 @@ unitTest(async function fileReaderLoadBlob(): Promise<void> {
   });
 });
 
-unitTest(async function fileReaderLoadBlobDouble(): Promise<void> {
+unitTest(async function fileReaderLoadBlobDouble() {
   // impl note from https://w3c.github.io/FileAPI/
   // Event handler for the load or error events could have started another load,
   // if that happens the loadend event for the first load is not fired
@@ -89,7 +89,7 @@ unitTest(async function fileReaderLoadBlobDouble(): Promise<void> {
   await new Promise<void>((resolve) => {
     let result: string | null = null;
 
-    fr.onload = (): void => {
+    fr.onload = () => {
       result = fr.result as string;
       assertEquals(result === "First load" || result === "Second load", true);
 
@@ -97,7 +97,7 @@ unitTest(async function fileReaderLoadBlobDouble(): Promise<void> {
         fr.readAsText(b2);
       }
     };
-    fr.onloadend = (): void => {
+    fr.onloadend = () => {
       assertEquals(result, "Second load");
 
       resolve();
@@ -107,13 +107,13 @@ unitTest(async function fileReaderLoadBlobDouble(): Promise<void> {
   });
 });
 
-unitTest(async function fileReaderLoadBlobArrayBuffer(): Promise<void> {
+unitTest(async function fileReaderLoadBlobArrayBuffer() {
   await new Promise<void>((resolve) => {
     const fr = new FileReader();
     const b1 = new Blob(["Hello World"]);
     let result: ArrayBuffer | null = null;
 
-    fr.onloadend = (ev): void => {
+    fr.onloadend = (ev) => {
       assertEquals(fr.result instanceof ArrayBuffer, true);
       result = fr.result as ArrayBuffer;
 
@@ -129,13 +129,13 @@ unitTest(async function fileReaderLoadBlobArrayBuffer(): Promise<void> {
   });
 });
 
-unitTest(async function fileReaderLoadBlobDataUrl(): Promise<void> {
+unitTest(async function fileReaderLoadBlobDataUrl() {
   await new Promise<void>((resolve) => {
     const fr = new FileReader();
     const b1 = new Blob(["Hello World"]);
     let result: string | null = null;
 
-    fr.onloadend = (ev): void => {
+    fr.onloadend = (ev) => {
       result = fr.result as string;
       assertEquals(
         result,
@@ -149,7 +149,7 @@ unitTest(async function fileReaderLoadBlobDataUrl(): Promise<void> {
   });
 });
 
-unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
+unitTest(async function fileReaderLoadBlobAbort() {
   await new Promise<void>((resolve) => {
     const fr = new FileReader();
     const b1 = new Blob(["Hello World"]);
@@ -160,10 +160,10 @@ unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
       abort: false,
     };
 
-    fr.onload = (): void => {
+    fr.onload = () => {
       hasOnEvents.load = true;
     };
-    fr.onloadend = (ev): void => {
+    fr.onloadend = (ev) => {
       hasOnEvents.loadend = true;
 
       assertEquals(hasOnEvents.load, false);
@@ -175,7 +175,7 @@ unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
       assertEquals(ev.lengthComputable, false);
       resolve();
     };
-    fr.onabort = (): void => {
+    fr.onabort = () => {
       hasOnEvents.abort = true;
     };
 
@@ -184,7 +184,7 @@ unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
   });
 });
 
-unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
+unitTest(async function fileReaderLoadBlobAbort() {
   await new Promise<void>((resolve) => {
     const fr = new FileReader();
     const b1 = new Blob(["Hello World"]);
@@ -195,10 +195,10 @@ unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
       abort: false,
     };
 
-    fr.onload = (): void => {
+    fr.onload = () => {
       hasOnEvents.load = true;
     };
-    fr.onloadend = (ev): void => {
+    fr.onloadend = (ev) => {
       hasOnEvents.loadend = true;
 
       assertEquals(hasOnEvents.load, false);
@@ -210,7 +210,7 @@ unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
       assertEquals(ev.lengthComputable, false);
       resolve();
     };
-    fr.onabort = (): void => {
+    fr.onabort = () => {
       hasOnEvents.abort = true;
     };
 
@@ -220,7 +220,7 @@ unitTest(async function fileReaderLoadBlobAbort(): Promise<void> {
 });
 
 unitTest(
-  async function fileReaderDispatchesEventsInCorrectOrder(): Promise<void> {
+  async function fileReaderDispatchesEventsInCorrectOrder() {
     await new Promise<void>((resolve) => {
       const fr = new FileReader();
       const b1 = new Blob(["Hello World"]);
@@ -228,7 +228,7 @@ unitTest(
       fr.addEventListener("loadend", () => {
         out += "1";
       });
-      fr.onloadend = (_ev): void => {
+      fr.onloadend = (_ev) => {
         out += "2";
       };
       fr.addEventListener("loadend", () => {
diff --git a/cli/tests/unit/files_test.ts b/cli/tests/unit/files_test.ts
index 348d012b4..a409434c1 100644
--- a/cli/tests/unit/files_test.ts
+++ b/cli/tests/unit/files_test.ts
@@ -10,15 +10,13 @@ import {
 } from "./test_util.ts";
 import { copy } from "../../../test_util/std/io/util.ts";
 
-unitTest(function filesStdioFileDescriptors(): void {
+unitTest(function filesStdioFileDescriptors() {
   assertEquals(Deno.stdin.rid, 0);
   assertEquals(Deno.stdout.rid, 1);
   assertEquals(Deno.stderr.rid, 2);
 });
 
-unitTest({ perms: { read: true } }, async function filesCopyToStdout(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function filesCopyToStdout() {
   const filename = "cli/tests/fixture.json";
   const file = await Deno.open(filename);
   assert(file.rid > 2);
@@ -28,7 +26,7 @@ unitTest({ perms: { read: true } }, async function filesCopyToStdout(): Promise<
   file.close();
 });
 
-unitTest({ perms: { read: true } }, async function filesIter(): Promise<void> {
+unitTest({ perms: { read: true } }, async function filesIter() {
   const filename = "cli/tests/hello.txt";
   const file = await Deno.open(filename);
 
@@ -43,7 +41,7 @@ unitTest({ perms: { read: true } }, async function filesIter(): Promise<void> {
 
 unitTest(
   { perms: { read: true } },
-  async function filesIterCustomBufSize(): Promise<void> {
+  async function filesIterCustomBufSize() {
     const filename = "cli/tests/hello.txt";
     const file = await Deno.open(filename);
 
@@ -60,7 +58,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: true } }, function filesIterSync(): void {
+unitTest({ perms: { read: true } }, function filesIterSync() {
   const filename = "cli/tests/hello.txt";
   const file = Deno.openSync(filename);
 
@@ -75,7 +73,7 @@ unitTest({ perms: { read: true } }, function filesIterSync(): void {
 
 unitTest(
   { perms: { read: true } },
-  function filesIterSyncCustomBufSize(): void {
+  function filesIterSyncCustomBufSize() {
     const filename = "cli/tests/hello.txt";
     const file = Deno.openSync(filename);
 
@@ -92,7 +90,7 @@ unitTest(
   },
 );
 
-unitTest(async function readerIter(): Promise<void> {
+unitTest(async function readerIter() {
   // ref: https://github.com/denoland/deno/issues/2330
   const encoder = new TextEncoder();
 
@@ -127,7 +125,7 @@ unitTest(async function readerIter(): Promise<void> {
   assertEquals(totalSize, 12);
 });
 
-unitTest(async function readerIterSync(): Promise<void> {
+unitTest(async function readerIterSync() {
   // ref: https://github.com/denoland/deno/issues/2330
   const encoder = new TextEncoder();
 
@@ -166,7 +164,7 @@ unitTest(
   {
     perms: { read: true, write: true },
   },
-  function openSyncMode(): void {
+  function openSyncMode() {
     const path = Deno.makeTempDirSync() + "/test_openSync.txt";
     const file = Deno.openSync(path, {
       write: true,
@@ -185,7 +183,7 @@ unitTest(
   {
     perms: { read: true, write: true },
   },
-  async function openMode(): Promise<void> {
+  async function openMode() {
     const path = (await Deno.makeTempDir()) + "/test_open.txt";
     const file = await Deno.open(path, {
       write: true,
@@ -204,7 +202,7 @@ unitTest(
   {
     perms: { read: true, write: true },
   },
-  function openSyncUrl(): void {
+  function openSyncUrl() {
     const tempDir = Deno.makeTempDirSync();
     const fileUrl = new URL(
       `file://${
@@ -230,7 +228,7 @@ unitTest(
   {
     perms: { read: true, write: true },
   },
-  async function openUrl(): Promise<void> {
+  async function openUrl() {
     const tempDir = await Deno.makeTempDir();
     const fileUrl = new URL(
       `file://${
@@ -254,7 +252,7 @@ unitTest(
 
 unitTest(
   { perms: { write: false } },
-  async function writePermFailure(): Promise<void> {
+  async function writePermFailure() {
     const filename = "tests/hello.txt";
     const openOptions: Deno.OpenOptions[] = [{ write: true }, { append: true }];
     for (const options of openOptions) {
@@ -265,10 +263,10 @@ unitTest(
   },
 );
 
-unitTest(async function openOptions(): Promise<void> {
+unitTest(async function openOptions() {
   const filename = "cli/tests/fixture.json";
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await Deno.open(filename, { write: false });
     },
     Error,
@@ -276,7 +274,7 @@ unitTest(async function openOptions(): Promise<void> {
   );
 
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await Deno.open(filename, { truncate: true, write: false });
     },
     Error,
@@ -284,7 +282,7 @@ unitTest(async function openOptions(): Promise<void> {
   );
 
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await Deno.open(filename, { create: true, write: false });
     },
     Error,
@@ -292,7 +290,7 @@ unitTest(async function openOptions(): Promise<void> {
   );
 
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await Deno.open(filename, { createNew: true, append: false });
     },
     Error,
@@ -300,9 +298,7 @@ unitTest(async function openOptions(): Promise<void> {
   );
 });
 
-unitTest({ perms: { read: false } }, async function readPermFailure(): Promise<
-  void
-> {
+unitTest({ perms: { read: false } }, async function readPermFailure() {
   await assertThrowsAsync(async () => {
     await Deno.open("package.json", { read: true });
   }, Deno.errors.PermissionDenied);
@@ -310,7 +306,7 @@ unitTest({ perms: { read: false } }, async function readPermFailure(): Promise<
 
 unitTest(
   { perms: { write: true } },
-  async function writeNullBufferFailure(): Promise<void> {
+  async function writeNullBufferFailure() {
     const tempDir = Deno.makeTempDirSync();
     const filename = tempDir + "hello.txt";
     const w = {
@@ -322,7 +318,7 @@ unitTest(
 
     // writing null should throw an error
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         // deno-lint-ignore no-explicit-any
         await file.write(null as any);
       },
@@ -334,7 +330,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function readNullBufferFailure(): Promise<void> {
+  async function readNullBufferFailure() {
     const tempDir = Deno.makeTempDirSync();
     const filename = tempDir + "hello.txt";
     const file = await Deno.open(filename, {
@@ -362,7 +358,7 @@ unitTest(
 
 unitTest(
   { perms: { write: false, read: false } },
-  async function readWritePermFailure(): Promise<void> {
+  async function readWritePermFailure() {
     const filename = "tests/hello.txt";
     await assertThrowsAsync(async () => {
       await Deno.open(filename, { read: true });
@@ -372,7 +368,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function createFile(): Promise<void> {
+  async function createFile() {
     const tempDir = await Deno.makeTempDir();
     const filename = tempDir + "/test.txt";
     const f = await Deno.create(filename);
@@ -393,7 +389,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function createFileWithUrl(): Promise<void> {
+  async function createFileWithUrl() {
     const tempDir = await Deno.makeTempDir();
     const fileUrl = new URL(
       `file://${Deno.build.os === "windows" ? "/" : ""}${tempDir}/test.txt`,
@@ -415,7 +411,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function createSyncFile(): Promise<void> {
+  async function createSyncFile() {
     const tempDir = await Deno.makeTempDir();
     const filename = tempDir + "/test.txt";
     const f = Deno.createSync(filename);
@@ -436,7 +432,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function createSyncFileWithUrl(): Promise<void> {
+  async function createSyncFileWithUrl() {
     const tempDir = await Deno.makeTempDir();
     const fileUrl = new URL(
       `file://${Deno.build.os === "windows" ? "/" : ""}${tempDir}/test.txt`,
@@ -458,7 +454,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function openModeWrite(): Promise<void> {
+  async function openModeWrite() {
     const tempDir = Deno.makeTempDirSync();
     const encoder = new TextEncoder();
     const filename = tempDir + "hello.txt";
@@ -501,7 +497,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function openModeWriteRead(): Promise<void> {
+  async function openModeWriteRead() {
     const tempDir = Deno.makeTempDirSync();
     const encoder = new TextEncoder();
     const filename = tempDir + "hello.txt";
@@ -535,7 +531,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: true } }, async function seekStart(): Promise<void> {
+unitTest({ perms: { read: true } }, async function seekStart() {
   const filename = "cli/tests/hello.txt";
   const file = await Deno.open(filename);
   const seekPosition = 6;
@@ -552,7 +548,7 @@ unitTest({ perms: { read: true } }, async function seekStart(): Promise<void> {
   file.close();
 });
 
-unitTest({ perms: { read: true } }, function seekSyncStart(): void {
+unitTest({ perms: { read: true } }, function seekSyncStart() {
   const filename = "cli/tests/hello.txt";
   const file = Deno.openSync(filename);
   const seekPosition = 6;
@@ -569,9 +565,7 @@ unitTest({ perms: { read: true } }, function seekSyncStart(): void {
   file.close();
 });
 
-unitTest({ perms: { read: true } }, async function seekCurrent(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function seekCurrent() {
   const filename = "cli/tests/hello.txt";
   const file = await Deno.open(filename);
   // Deliberately move 1 step forward
@@ -588,7 +582,7 @@ unitTest({ perms: { read: true } }, async function seekCurrent(): Promise<
   file.close();
 });
 
-unitTest({ perms: { read: true } }, function seekSyncCurrent(): void {
+unitTest({ perms: { read: true } }, function seekSyncCurrent() {
   const filename = "cli/tests/hello.txt";
   const file = Deno.openSync(filename);
   // Deliberately move 1 step forward
@@ -605,7 +599,7 @@ unitTest({ perms: { read: true } }, function seekSyncCurrent(): void {
   file.close();
 });
 
-unitTest({ perms: { read: true } }, async function seekEnd(): Promise<void> {
+unitTest({ perms: { read: true } }, async function seekEnd() {
   const filename = "cli/tests/hello.txt";
   const file = await Deno.open(filename);
   const seekPosition = -6;
@@ -619,7 +613,7 @@ unitTest({ perms: { read: true } }, async function seekEnd(): Promise<void> {
   file.close();
 });
 
-unitTest({ perms: { read: true } }, function seekSyncEnd(): void {
+unitTest({ perms: { read: true } }, function seekSyncEnd() {
   const filename = "cli/tests/hello.txt";
   const file = Deno.openSync(filename);
   const seekPosition = -6;
@@ -633,11 +627,11 @@ unitTest({ perms: { read: true } }, function seekSyncEnd(): void {
   file.close();
 });
 
-unitTest({ perms: { read: true } }, async function seekMode(): Promise<void> {
+unitTest({ perms: { read: true } }, async function seekMode() {
   const filename = "cli/tests/hello.txt";
   const file = await Deno.open(filename);
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await file.seek(1, -1);
     },
     TypeError,
diff --git a/cli/tests/unit/fs_events_test.ts b/cli/tests/unit/fs_events_test.ts
index 87f3ec241..7c944a4e8 100644
--- a/cli/tests/unit/fs_events_test.ts
+++ b/cli/tests/unit/fs_events_test.ts
@@ -38,7 +38,7 @@ async function getTwoEvents(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function watchFsBasic(): Promise<void> {
+  async function watchFsBasic() {
     const testDir = await Deno.makeTempDir();
     const iter = Deno.watchFs(testDir);
 
@@ -65,7 +65,7 @@ unitTest(
 // This should be removed at 2.0
 unitTest(
   { perms: { read: true, write: true } },
-  async function watchFsReturn(): Promise<void> {
+  async function watchFsReturn() {
     const testDir = await Deno.makeTempDir();
     const iter = Deno.watchFs(testDir);
 
@@ -83,7 +83,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function watchFsClose(): Promise<void> {
+  async function watchFsClose() {
     const testDir = await Deno.makeTempDir();
     const iter = Deno.watchFs(testDir);
 
diff --git a/cli/tests/unit/get_random_values_test.ts b/cli/tests/unit/get_random_values_test.ts
index 3f9f311f6..a9b493104 100644
--- a/cli/tests/unit/get_random_values_test.ts
+++ b/cli/tests/unit/get_random_values_test.ts
@@ -1,49 +1,49 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertNotEquals, assertStrictEquals, unitTest } from "./test_util.ts";
 
-unitTest(function getRandomValuesInt8Array(): void {
+unitTest(function getRandomValuesInt8Array() {
   const arr = new Int8Array(32);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Int8Array(32));
 });
 
-unitTest(function getRandomValuesUint8Array(): void {
+unitTest(function getRandomValuesUint8Array() {
   const arr = new Uint8Array(32);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Uint8Array(32));
 });
 
-unitTest(function getRandomValuesUint8ClampedArray(): void {
+unitTest(function getRandomValuesUint8ClampedArray() {
   const arr = new Uint8ClampedArray(32);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Uint8ClampedArray(32));
 });
 
-unitTest(function getRandomValuesInt16Array(): void {
+unitTest(function getRandomValuesInt16Array() {
   const arr = new Int16Array(4);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Int16Array(4));
 });
 
-unitTest(function getRandomValuesUint16Array(): void {
+unitTest(function getRandomValuesUint16Array() {
   const arr = new Uint16Array(4);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Uint16Array(4));
 });
 
-unitTest(function getRandomValuesInt32Array(): void {
+unitTest(function getRandomValuesInt32Array() {
   const arr = new Int32Array(8);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Int32Array(8));
 });
 
-unitTest(function getRandomValuesUint32Array(): void {
+unitTest(function getRandomValuesUint32Array() {
   const arr = new Uint32Array(8);
   crypto.getRandomValues(arr);
   assertNotEquals(arr, new Uint32Array(8));
 });
 
-unitTest(function getRandomValuesReturnValue(): void {
+unitTest(function getRandomValuesReturnValue() {
   const arr = new Uint32Array(8);
   const rtn = crypto.getRandomValues(arr);
   assertNotEquals(arr, new Uint32Array(8));
diff --git a/cli/tests/unit/globals_test.ts b/cli/tests/unit/globals_test.ts
index 08ae23765..0051dce49 100644
--- a/cli/tests/unit/globals_test.ts
+++ b/cli/tests/unit/globals_test.ts
@@ -1,72 +1,72 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, unitTest } from "./test_util.ts";
 
-unitTest(function globalThisExists(): void {
+unitTest(function globalThisExists() {
   assert(globalThis != null);
 });
 
-unitTest(function noInternalGlobals(): void {
+unitTest(function noInternalGlobals() {
   // globalThis.__bootstrap should not be there.
   for (const key of Object.keys(globalThis)) {
     assert(!key.startsWith("_"));
   }
 });
 
-unitTest(function windowExists(): void {
+unitTest(function windowExists() {
   assert(window != null);
 });
 
-unitTest(function selfExists(): void {
+unitTest(function selfExists() {
   assert(self != null);
 });
 
-unitTest(function windowWindowExists(): void {
+unitTest(function windowWindowExists() {
   assert(window.window === window);
 });
 
-unitTest(function windowSelfExists(): void {
+unitTest(function windowSelfExists() {
   assert(window.self === window);
 });
 
-unitTest(function globalThisEqualsWindow(): void {
+unitTest(function globalThisEqualsWindow() {
   assert(globalThis === window);
 });
 
-unitTest(function globalThisEqualsSelf(): void {
+unitTest(function globalThisEqualsSelf() {
   assert(globalThis === self);
 });
 
-unitTest(function globalThisInstanceofWindow(): void {
+unitTest(function globalThisInstanceofWindow() {
   assert(globalThis instanceof Window);
 });
 
-unitTest(function globalThisConstructorLength(): void {
+unitTest(function globalThisConstructorLength() {
   assert(globalThis.constructor.length === 0);
 });
 
-unitTest(function globalThisInstanceofEventTarget(): void {
+unitTest(function globalThisInstanceofEventTarget() {
   assert(globalThis instanceof EventTarget);
 });
 
-unitTest(function navigatorInstanceofNavigator(): void {
+unitTest(function navigatorInstanceofNavigator() {
   // TODO(nayeemrmn): Add `Navigator` to deno_lint globals.
   // deno-lint-ignore no-undef
   assert(navigator instanceof Navigator);
 });
 
-unitTest(function DenoNamespaceExists(): void {
+unitTest(function DenoNamespaceExists() {
   assert(Deno != null);
 });
 
-unitTest(function DenoNamespaceEqualsWindowDeno(): void {
+unitTest(function DenoNamespaceEqualsWindowDeno() {
   assert(Deno === window.Deno);
 });
 
-unitTest(function DenoNamespaceIsNotFrozen(): void {
+unitTest(function DenoNamespaceIsNotFrozen() {
   assert(!Object.isFrozen(Deno));
 });
 
-unitTest(function webAssemblyExists(): void {
+unitTest(function webAssemblyExists() {
   assert(typeof WebAssembly.compile === "function");
 });
 
@@ -84,7 +84,7 @@ unitTest(function DenoNamespaceConfigurable() {
   assert(!desc.writable);
 });
 
-unitTest(function DenoCoreNamespaceIsImmutable(): void {
+unitTest(function DenoCoreNamespaceIsImmutable() {
   const { print } = Deno.core;
   try {
     Deno.core.print = 1;
@@ -100,18 +100,18 @@ unitTest(function DenoCoreNamespaceIsImmutable(): void {
   assert(print === Deno.core.print);
 });
 
-unitTest(async function windowQueueMicrotask(): Promise<void> {
+unitTest(async function windowQueueMicrotask() {
   let resolve1: () => void | undefined;
   let resolve2: () => void | undefined;
   let microtaskDone = false;
-  const p1 = new Promise<void>((res): void => {
-    resolve1 = (): void => {
+  const p1 = new Promise<void>((res) => {
+    resolve1 = () => {
       microtaskDone = true;
       res();
     };
   });
-  const p2 = new Promise<void>((res): void => {
-    resolve2 = (): void => {
+  const p2 = new Promise<void>((res) => {
+    resolve2 = () => {
       assert(microtaskDone);
       res();
     };
diff --git a/cli/tests/unit/headers_test.ts b/cli/tests/unit/headers_test.ts
index c79673d84..bc695e7d9 100644
--- a/cli/tests/unit/headers_test.ts
+++ b/cli/tests/unit/headers_test.ts
@@ -5,14 +5,14 @@ const {
   // @ts-expect-error TypeScript (as of 3.7) does not support indexing namespaces by symbol
 } = Deno[Deno.internal];
 
-unitTest(function headersHasCorrectNameProp(): void {
+unitTest(function headersHasCorrectNameProp() {
   assertEquals(Headers.name, "Headers");
 });
 
 // Logic heavily copied from web-platform-tests, make
 // sure pass mostly header basic test
 // ref: https://github.com/web-platform-tests/wpt/blob/7c50c216081d6ea3c9afe553ee7b64534020a1b2/fetch/api/headers/headers-basic.html
-unitTest(function newHeaderTest(): void {
+unitTest(function newHeaderTest() {
   new Headers();
   new Headers(undefined);
   new Headers({});
@@ -38,7 +38,7 @@ for (const name in headerDict) {
   headerSeq.push([name, headerDict[name]]);
 }
 
-unitTest(function newHeaderWithSequence(): void {
+unitTest(function newHeaderWithSequence() {
   const headers = new Headers(headerSeq);
   for (const name in headerDict) {
     assertEquals(headers.get(name), String(headerDict[name]));
@@ -46,14 +46,14 @@ unitTest(function newHeaderWithSequence(): void {
   assertEquals(headers.get("length"), null);
 });
 
-unitTest(function newHeaderWithRecord(): void {
+unitTest(function newHeaderWithRecord() {
   const headers = new Headers(headerDict);
   for (const name in headerDict) {
     assertEquals(headers.get(name), String(headerDict[name]));
   }
 });
 
-unitTest(function newHeaderWithHeadersInstance(): void {
+unitTest(function newHeaderWithHeadersInstance() {
   const headers = new Headers(headerDict);
   const headers2 = new Headers(headers);
   for (const name in headerDict) {
@@ -61,7 +61,7 @@ unitTest(function newHeaderWithHeadersInstance(): void {
   }
 });
 
-unitTest(function headerAppendSuccess(): void {
+unitTest(function headerAppendSuccess() {
   const headers = new Headers();
   for (const name in headerDict) {
     headers.append(name, headerDict[name]);
@@ -69,7 +69,7 @@ unitTest(function headerAppendSuccess(): void {
   }
 });
 
-unitTest(function headerSetSuccess(): void {
+unitTest(function headerSetSuccess() {
   const headers = new Headers();
   for (const name in headerDict) {
     headers.set(name, headerDict[name]);
@@ -77,7 +77,7 @@ unitTest(function headerSetSuccess(): void {
   }
 });
 
-unitTest(function headerHasSuccess(): void {
+unitTest(function headerHasSuccess() {
   const headers = new Headers(headerDict);
   for (const name in headerDict) {
     assert(headers.has(name), "headers has name " + name);
@@ -88,7 +88,7 @@ unitTest(function headerHasSuccess(): void {
   }
 });
 
-unitTest(function headerDeleteSuccess(): void {
+unitTest(function headerDeleteSuccess() {
   const headers = new Headers(headerDict);
   for (const name in headerDict) {
     assert(headers.has(name), "headers have a header: " + name);
@@ -97,7 +97,7 @@ unitTest(function headerDeleteSuccess(): void {
   }
 });
 
-unitTest(function headerGetSuccess(): void {
+unitTest(function headerGetSuccess() {
   const headers = new Headers(headerDict);
   for (const name in headerDict) {
     assertEquals(headers.get(name), String(headerDict[name]));
@@ -105,7 +105,7 @@ unitTest(function headerGetSuccess(): void {
   }
 });
 
-unitTest(function headerEntriesSuccess(): void {
+unitTest(function headerEntriesSuccess() {
   const headers = new Headers(headerDict);
   const iterators = headers.entries();
   for (const it of iterators) {
@@ -116,7 +116,7 @@ unitTest(function headerEntriesSuccess(): void {
   }
 });
 
-unitTest(function headerKeysSuccess(): void {
+unitTest(function headerKeysSuccess() {
   const headers = new Headers(headerDict);
   const iterators = headers.keys();
   for (const it of iterators) {
@@ -124,7 +124,7 @@ unitTest(function headerKeysSuccess(): void {
   }
 });
 
-unitTest(function headerValuesSuccess(): void {
+unitTest(function headerValuesSuccess() {
   const headers = new Headers(headerDict);
   const iterators = headers.values();
   const entries = headers.entries();
@@ -146,16 +146,16 @@ const headerEntriesDict: Record<string, string> = {
   "Content-Types": "value6",
 };
 
-unitTest(function headerForEachSuccess(): void {
+unitTest(function headerForEachSuccess() {
   const headers = new Headers(headerEntriesDict);
   const keys = Object.keys(headerEntriesDict);
-  keys.forEach((key): void => {
+  keys.forEach((key) => {
     const value = headerEntriesDict[key];
     const newkey = key.toLowerCase();
     headerEntriesDict[newkey] = value;
   });
   let callNum = 0;
-  headers.forEach((value, key, container): void => {
+  headers.forEach((value, key, container) => {
     assertEquals(headers, container);
     assertEquals(value, headerEntriesDict[key]);
     callNum++;
@@ -163,7 +163,7 @@ unitTest(function headerForEachSuccess(): void {
   assertEquals(callNum, keys.length);
 });
 
-unitTest(function headerSymbolIteratorSuccess(): void {
+unitTest(function headerSymbolIteratorSuccess() {
   assert(Symbol.iterator in Headers.prototype);
   const headers = new Headers(headerEntriesDict);
   for (const header of headers) {
@@ -174,7 +174,7 @@ unitTest(function headerSymbolIteratorSuccess(): void {
   }
 });
 
-unitTest(function headerTypesAvailable(): void {
+unitTest(function headerTypesAvailable() {
   function newHeaders(): Headers {
     return new Headers();
   }
@@ -184,7 +184,7 @@ unitTest(function headerTypesAvailable(): void {
 
 // Modified from https://github.com/bitinn/node-fetch/blob/7d3293200a91ad52b5ca7962f9d6fd1c04983edb/test/test.js#L2001-L2014
 // Copyright (c) 2016 David Frank. MIT License.
-unitTest(function headerIllegalReject(): void {
+unitTest(function headerIllegalReject() {
   let errorCount = 0;
   try {
     new Headers({ "He y": "ok" });
@@ -238,7 +238,7 @@ unitTest(function headerIllegalReject(): void {
 });
 
 // If pair does not contain exactly two items,then throw a TypeError.
-unitTest(function headerParamsShouldThrowTypeError(): void {
+unitTest(function headerParamsShouldThrowTypeError() {
   let hasThrown = 0;
 
   try {
@@ -255,12 +255,12 @@ unitTest(function headerParamsShouldThrowTypeError(): void {
   assertEquals(hasThrown, 2);
 });
 
-unitTest(function headerParamsArgumentsCheck(): void {
+unitTest(function headerParamsArgumentsCheck() {
   const methodRequireOneParam = ["delete", "get", "has", "forEach"] as const;
 
   const methodRequireTwoParams = ["append", "set"] as const;
 
-  methodRequireOneParam.forEach((method): void => {
+  methodRequireOneParam.forEach((method) => {
     const headers = new Headers();
     let hasThrown = 0;
     try {
@@ -277,7 +277,7 @@ unitTest(function headerParamsArgumentsCheck(): void {
     assertEquals(hasThrown, 2);
   });
 
-  methodRequireTwoParams.forEach((method): void => {
+  methodRequireTwoParams.forEach((method) => {
     const headers = new Headers();
     let hasThrown = 0;
 
@@ -310,7 +310,7 @@ unitTest(function headerParamsArgumentsCheck(): void {
   });
 });
 
-unitTest(function headersInitMultiple(): void {
+unitTest(function headersInitMultiple() {
   const headers = new Headers([
     ["Set-Cookie", "foo=bar"],
     ["Set-Cookie", "bar=baz"],
@@ -325,7 +325,7 @@ unitTest(function headersInitMultiple(): void {
   ]);
 });
 
-unitTest(function headersAppendMultiple(): void {
+unitTest(function headersAppendMultiple() {
   const headers = new Headers([
     ["Set-Cookie", "foo=bar"],
     ["X-Deno", "foo"],
@@ -340,7 +340,7 @@ unitTest(function headersAppendMultiple(): void {
   ]);
 });
 
-unitTest(function headersAppendDuplicateSetCookieKey(): void {
+unitTest(function headersAppendDuplicateSetCookieKey() {
   const headers = new Headers([["Set-Cookie", "foo=bar"]]);
   headers.append("set-Cookie", "foo=baz");
   headers.append("Set-cookie", "baz=bar");
@@ -352,7 +352,7 @@ unitTest(function headersAppendDuplicateSetCookieKey(): void {
   ]);
 });
 
-unitTest(function headersGetSetCookie(): void {
+unitTest(function headersGetSetCookie() {
   const headers = new Headers([
     ["Set-Cookie", "foo=bar"],
     ["set-Cookie", "bar=qat"],
@@ -360,7 +360,7 @@ unitTest(function headersGetSetCookie(): void {
   assertEquals(headers.get("SET-COOKIE"), "foo=bar, bar=qat");
 });
 
-unitTest(function toStringShouldBeWebCompatibility(): void {
+unitTest(function toStringShouldBeWebCompatibility() {
   const headers = new Headers();
   assertEquals(headers.toString(), "[object Headers]");
 });
@@ -369,7 +369,7 @@ function stringify(...args: unknown[]): string {
   return inspectArgs(args).replace(/\n$/, "");
 }
 
-unitTest(function customInspectReturnsCorrectHeadersFormat(): void {
+unitTest(function customInspectReturnsCorrectHeadersFormat() {
   const blankHeaders = new Headers();
   assertEquals(stringify(blankHeaders), "Headers {}");
   const singleHeader = new Headers([["Content-Type", "application/json"]]);
diff --git a/cli/tests/unit/http_test.ts b/cli/tests/unit/http_test.ts
index 3232d3f27..ffd29ff86 100644
--- a/cli/tests/unit/http_test.ts
+++ b/cli/tests/unit/http_test.ts
@@ -200,7 +200,7 @@ unitTest({ perms: { net: true } }, async function httpServerInvalidMethod() {
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function httpServerWithTls(): Promise<void> {
+  async function httpServerWithTls() {
     const hostname = "localhost";
     const port = 4501;
 
diff --git a/cli/tests/unit/internals_test.ts b/cli/tests/unit/internals_test.ts
index 9a5820dec..d3512de05 100644
--- a/cli/tests/unit/internals_test.ts
+++ b/cli/tests/unit/internals_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, unitTest } from "./test_util.ts";
 
-unitTest(function internalsExists(): void {
+unitTest(function internalsExists() {
   const {
     inspectArgs,
     // @ts-expect-error TypeScript (as of 3.7) does not support indexing namespaces by symbol
diff --git a/cli/tests/unit/link_test.ts b/cli/tests/unit/link_test.ts
index 86cd65bae..5d3553ac3 100644
--- a/cli/tests/unit/link_test.ts
+++ b/cli/tests/unit/link_test.ts
@@ -3,7 +3,7 @@ import { assert, assertEquals, assertThrows, unitTest } from "./test_util.ts";
 
 unitTest(
   { perms: { read: true, write: true } },
-  function linkSyncSuccess(): void {
+  function linkSyncSuccess() {
     const testDir = Deno.makeTempDirSync();
     const oldData = "Hardlink";
     const oldName = testDir + "/oldname";
@@ -42,7 +42,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function linkSyncExists(): void {
+  function linkSyncExists() {
     const testDir = Deno.makeTempDirSync();
     const oldName = testDir + "/oldname";
     const newName = testDir + "/newname";
@@ -58,7 +58,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function linkSyncNotFound(): void {
+  function linkSyncNotFound() {
     const testDir = Deno.makeTempDirSync();
     const oldName = testDir + "/oldname";
     const newName = testDir + "/newname";
@@ -71,7 +71,7 @@ unitTest(
 
 unitTest(
   { perms: { read: false, write: true } },
-  function linkSyncReadPerm(): void {
+  function linkSyncReadPerm() {
     assertThrows(() => {
       Deno.linkSync("oldbaddir", "newbaddir");
     }, Deno.errors.PermissionDenied);
@@ -80,7 +80,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: false } },
-  function linkSyncWritePerm(): void {
+  function linkSyncWritePerm() {
     assertThrows(() => {
       Deno.linkSync("oldbaddir", "newbaddir");
     }, Deno.errors.PermissionDenied);
@@ -89,7 +89,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function linkSuccess(): Promise<void> {
+  async function linkSuccess() {
     const testDir = Deno.makeTempDirSync();
     const oldData = "Hardlink";
     const oldName = testDir + "/oldname";
diff --git a/cli/tests/unit/make_temp_test.ts b/cli/tests/unit/make_temp_test.ts
index b43d257e0..5b28c210b 100644
--- a/cli/tests/unit/make_temp_test.ts
+++ b/cli/tests/unit/make_temp_test.ts
@@ -7,7 +7,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { write: true } }, function makeTempDirSyncSuccess(): void {
+unitTest({ perms: { write: true } }, function makeTempDirSyncSuccess() {
   const dir1 = Deno.makeTempDirSync({ prefix: "hello", suffix: "world" });
   const dir2 = Deno.makeTempDirSync({ prefix: "hello", suffix: "world" });
   // Check that both dirs are different.
@@ -30,7 +30,7 @@ unitTest({ perms: { write: true } }, function makeTempDirSyncSuccess(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function makeTempDirSyncMode(): void {
+  function makeTempDirSyncMode() {
     const path = Deno.makeTempDirSync();
     const pathInfo = Deno.statSync(path);
     if (Deno.build.os !== "windows") {
@@ -39,7 +39,7 @@ unitTest(
   },
 );
 
-unitTest(function makeTempDirSyncPerm(): void {
+unitTest(function makeTempDirSyncPerm() {
   // makeTempDirSync should require write permissions (for now).
   assertThrows(() => {
     Deno.makeTempDirSync({ dir: "/baddir" });
@@ -48,7 +48,7 @@ unitTest(function makeTempDirSyncPerm(): void {
 
 unitTest(
   { perms: { write: true } },
-  async function makeTempDirSuccess(): Promise<void> {
+  async function makeTempDirSuccess() {
     const dir1 = await Deno.makeTempDir({ prefix: "hello", suffix: "world" });
     const dir2 = await Deno.makeTempDir({ prefix: "hello", suffix: "world" });
     // Check that both dirs are different.
@@ -72,7 +72,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function makeTempDirMode(): Promise<void> {
+  async function makeTempDirMode() {
     const path = await Deno.makeTempDir();
     const pathInfo = Deno.statSync(path);
     if (Deno.build.os !== "windows") {
@@ -81,7 +81,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: true } }, function makeTempFileSyncSuccess(): void {
+unitTest({ perms: { write: true } }, function makeTempFileSyncSuccess() {
   const file1 = Deno.makeTempFileSync({ prefix: "hello", suffix: "world" });
   const file2 = Deno.makeTempFileSync({ prefix: "hello", suffix: "world" });
   // Check that both dirs are different.
@@ -105,7 +105,7 @@ unitTest({ perms: { write: true } }, function makeTempFileSyncSuccess(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function makeTempFileSyncMode(): void {
+  function makeTempFileSyncMode() {
     const path = Deno.makeTempFileSync();
     const pathInfo = Deno.statSync(path);
     if (Deno.build.os !== "windows") {
@@ -114,7 +114,7 @@ unitTest(
   },
 );
 
-unitTest(function makeTempFileSyncPerm(): void {
+unitTest(function makeTempFileSyncPerm() {
   // makeTempFileSync should require write permissions (for now).
   assertThrows(() => {
     Deno.makeTempFileSync({ dir: "/baddir" });
@@ -123,7 +123,7 @@ unitTest(function makeTempFileSyncPerm(): void {
 
 unitTest(
   { perms: { write: true } },
-  async function makeTempFileSuccess(): Promise<void> {
+  async function makeTempFileSuccess() {
     const file1 = await Deno.makeTempFile({ prefix: "hello", suffix: "world" });
     const file2 = await Deno.makeTempFile({ prefix: "hello", suffix: "world" });
     // Check that both dirs are different.
@@ -148,7 +148,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function makeTempFileMode(): Promise<void> {
+  async function makeTempFileMode() {
     const path = await Deno.makeTempFile();
     const pathInfo = Deno.statSync(path);
     if (Deno.build.os !== "windows") {
diff --git a/cli/tests/unit/metrics_test.ts b/cli/tests/unit/metrics_test.ts
index f041cf1c9..d6a312e50 100644
--- a/cli/tests/unit/metrics_test.ts
+++ b/cli/tests/unit/metrics_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, unitTest } from "./test_util.ts";
 
-unitTest(async function metrics(): Promise<void> {
+unitTest(async function metrics() {
   // Write to stdout to ensure a "data" message gets sent instead of just
   // control messages.
   const dataMsg = new Uint8Array([13, 13, 13]); // "\r\r\r",
@@ -41,7 +41,7 @@ unitTest(async function metrics(): Promise<void> {
 
 unitTest(
   { perms: { write: true } },
-  function metricsUpdatedIfNoResponseSync(): void {
+  function metricsUpdatedIfNoResponseSync() {
     const filename = Deno.makeTempDirSync() + "/test.txt";
 
     const data = new Uint8Array([41, 42, 43]);
@@ -55,7 +55,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true } },
-  async function metricsUpdatedIfNoResponseAsync(): Promise<void> {
+  async function metricsUpdatedIfNoResponseAsync() {
     const filename = Deno.makeTempDirSync() + "/test.txt";
 
     const data = new Uint8Array([41, 42, 43]);
@@ -69,7 +69,7 @@ unitTest(
 );
 
 // Test that ops from extensions have metrics (via OpMiddleware)
-unitTest(function metricsForOpCrates(): void {
+unitTest(function metricsForOpCrates() {
   const _ = new URL("https://deno.land");
 
   const m1 = Deno.metrics().ops["op_url_parse"];
diff --git a/cli/tests/unit/mkdir_test.ts b/cli/tests/unit/mkdir_test.ts
index fd0328f57..586c1ebe3 100644
--- a/cli/tests/unit/mkdir_test.ts
+++ b/cli/tests/unit/mkdir_test.ts
@@ -8,7 +8,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-function assertDirectory(path: string, mode?: number): void {
+function assertDirectory(path: string, mode?: number) {
   const info = Deno.lstatSync(path);
   assert(info.isDirectory);
   if (Deno.build.os !== "windows" && mode !== undefined) {
@@ -18,7 +18,7 @@ function assertDirectory(path: string, mode?: number): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncSuccess(): void {
+  function mkdirSyncSuccess() {
     const path = Deno.makeTempDirSync() + "/dir";
     Deno.mkdirSync(path);
     assertDirectory(path);
@@ -27,14 +27,14 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncMode(): void {
+  function mkdirSyncMode() {
     const path = Deno.makeTempDirSync() + "/dir";
     Deno.mkdirSync(path, { mode: 0o737 });
     assertDirectory(path, 0o737);
   },
 );
 
-unitTest({ perms: { write: false } }, function mkdirSyncPerm(): void {
+unitTest({ perms: { write: false } }, function mkdirSyncPerm() {
   assertThrows(() => {
     Deno.mkdirSync("/baddir");
   }, Deno.errors.PermissionDenied);
@@ -42,7 +42,7 @@ unitTest({ perms: { write: false } }, function mkdirSyncPerm(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function mkdirSuccess(): Promise<void> {
+  async function mkdirSuccess() {
     const path = Deno.makeTempDirSync() + "/dir";
     await Deno.mkdir(path);
     assertDirectory(path);
@@ -51,22 +51,20 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function mkdirMode(): Promise<void> {
+  async function mkdirMode() {
     const path = Deno.makeTempDirSync() + "/dir";
     await Deno.mkdir(path, { mode: 0o737 });
     assertDirectory(path, 0o737);
   },
 );
 
-unitTest({ perms: { write: true } }, function mkdirErrSyncIfExists(): void {
+unitTest({ perms: { write: true } }, function mkdirErrSyncIfExists() {
   assertThrows(() => {
     Deno.mkdirSync(".");
   }, Deno.errors.AlreadyExists);
 });
 
-unitTest({ perms: { write: true } }, async function mkdirErrIfExists(): Promise<
-  void
-> {
+unitTest({ perms: { write: true } }, async function mkdirErrIfExists() {
   await assertThrowsAsync(async () => {
     await Deno.mkdir(".");
   }, Deno.errors.AlreadyExists);
@@ -74,7 +72,7 @@ unitTest({ perms: { write: true } }, async function mkdirErrIfExists(): Promise<
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncRecursive(): void {
+  function mkdirSyncRecursive() {
     const path = Deno.makeTempDirSync() + "/nested/directory";
     Deno.mkdirSync(path, { recursive: true });
     assertDirectory(path);
@@ -83,7 +81,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function mkdirRecursive(): Promise<void> {
+  async function mkdirRecursive() {
     const path = Deno.makeTempDirSync() + "/nested/directory";
     await Deno.mkdir(path, { recursive: true });
     assertDirectory(path);
@@ -92,7 +90,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncRecursiveMode(): void {
+  function mkdirSyncRecursiveMode() {
     const nested = Deno.makeTempDirSync() + "/nested";
     const path = nested + "/dir";
     Deno.mkdirSync(path, { mode: 0o737, recursive: true });
@@ -103,7 +101,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function mkdirRecursiveMode(): Promise<void> {
+  async function mkdirRecursiveMode() {
     const nested = Deno.makeTempDirSync() + "/nested";
     const path = nested + "/dir";
     await Deno.mkdir(path, { mode: 0o737, recursive: true });
@@ -114,7 +112,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncRecursiveIfExists(): void {
+  function mkdirSyncRecursiveIfExists() {
     const path = Deno.makeTempDirSync() + "/dir";
     Deno.mkdirSync(path, { mode: 0o737 });
     Deno.mkdirSync(path, { recursive: true });
@@ -132,7 +130,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function mkdirRecursiveIfExists(): Promise<void> {
+  async function mkdirRecursiveIfExists() {
     const path = Deno.makeTempDirSync() + "/dir";
     await Deno.mkdir(path, { mode: 0o737 });
     await Deno.mkdir(path, { recursive: true });
@@ -150,7 +148,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncErrors(): void {
+  function mkdirSyncErrors() {
     const testDir = Deno.makeTempDirSync();
     const emptydir = testDir + "/empty";
     const fulldir = testDir + "/dir";
@@ -159,16 +157,16 @@ unitTest(
     Deno.mkdirSync(fulldir);
     Deno.createSync(file).close();
 
-    assertThrows((): void => {
+    assertThrows(() => {
       Deno.mkdirSync(emptydir, { recursive: false });
     }, Deno.errors.AlreadyExists);
-    assertThrows((): void => {
+    assertThrows(() => {
       Deno.mkdirSync(fulldir, { recursive: false });
     }, Deno.errors.AlreadyExists);
-    assertThrows((): void => {
+    assertThrows(() => {
       Deno.mkdirSync(file, { recursive: false });
     }, Deno.errors.AlreadyExists);
-    assertThrows((): void => {
+    assertThrows(() => {
       Deno.mkdirSync(file, { recursive: true });
     }, Deno.errors.AlreadyExists);
 
@@ -180,19 +178,19 @@ unitTest(
       Deno.symlinkSync(emptydir, dirLink);
       Deno.symlinkSync(testDir + "/nonexistent", danglingLink);
 
-      assertThrows((): void => {
+      assertThrows(() => {
         Deno.mkdirSync(dirLink, { recursive: false });
       }, Deno.errors.AlreadyExists);
-      assertThrows((): void => {
+      assertThrows(() => {
         Deno.mkdirSync(fileLink, { recursive: false });
       }, Deno.errors.AlreadyExists);
-      assertThrows((): void => {
+      assertThrows(() => {
         Deno.mkdirSync(fileLink, { recursive: true });
       }, Deno.errors.AlreadyExists);
-      assertThrows((): void => {
+      assertThrows(() => {
         Deno.mkdirSync(danglingLink, { recursive: false });
       }, Deno.errors.AlreadyExists);
-      assertThrows((): void => {
+      assertThrows(() => {
         Deno.mkdirSync(danglingLink, { recursive: true });
       }, Deno.errors.AlreadyExists);
     }
@@ -201,7 +199,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function mkdirSyncRelativeUrlPath(): void {
+  function mkdirSyncRelativeUrlPath() {
     const testDir = Deno.makeTempDirSync();
     const nestedDir = testDir + "/nested";
     // Add trailing slash so base path is treated as a directory. pathToAbsoluteFileUrl removes trailing slashes.
@@ -216,7 +214,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function mkdirRelativeUrlPath(): Promise<void> {
+  async function mkdirRelativeUrlPath() {
     const testDir = Deno.makeTempDirSync();
     const nestedDir = testDir + "/nested";
     // Add trailing slash so base path is treated as a directory. pathToAbsoluteFileUrl removes trailing slashes.
diff --git a/cli/tests/unit/navigator_test.ts b/cli/tests/unit/navigator_test.ts
index 10475d973..6357d4c56 100644
--- a/cli/tests/unit/navigator_test.ts
+++ b/cli/tests/unit/navigator_test.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, unitTest } from "./test_util.ts";
 
-unitTest(function navigatorNumCpus(): void {
+unitTest(function navigatorNumCpus() {
   assert(navigator.hardwareConcurrency > 0);
 });
diff --git a/cli/tests/unit/net_test.ts b/cli/tests/unit/net_test.ts
index a7a9454c0..26175f121 100644
--- a/cli/tests/unit/net_test.ts
+++ b/cli/tests/unit/net_test.ts
@@ -10,7 +10,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { net: true } }, function netTcpListenClose(): void {
+unitTest({ perms: { net: true } }, function netTcpListenClose() {
   const listener = Deno.listen({ hostname: "127.0.0.1", port: 3500 });
   assert(listener.addr.transport === "tcp");
   assertEquals(listener.addr.hostname, "127.0.0.1");
@@ -23,7 +23,7 @@ unitTest(
   {
     perms: { net: true },
   },
-  function netUdpListenClose(): void {
+  function netUdpListenClose() {
     const socket = Deno.listenDatagram({
       hostname: "127.0.0.1",
       port: 3500,
@@ -38,7 +38,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  function netUnixListenClose(): void {
+  function netUnixListenClose() {
     const filePath = Deno.makeTempFileSync();
     const socket = Deno.listen({
       path: filePath,
@@ -52,7 +52,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  function netUnixPacketListenClose(): void {
+  function netUnixPacketListenClose() {
     const filePath = Deno.makeTempFileSync();
     const socket = Deno.listenDatagram({
       path: filePath,
@@ -66,7 +66,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true } },
-  function netUnixListenWritePermission(): void {
+  function netUnixListenWritePermission() {
     assertThrows(() => {
       const filePath = Deno.makeTempFileSync();
       const socket = Deno.listen({
@@ -82,7 +82,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true } },
-  function netUnixPacketListenWritePermission(): void {
+  function netUnixPacketListenWritePermission() {
     assertThrows(() => {
       const filePath = Deno.makeTempFileSync();
       const socket = Deno.listenDatagram({
@@ -100,12 +100,12 @@ unitTest(
   {
     perms: { net: true },
   },
-  async function netTcpCloseWhileAccept(): Promise<void> {
+  async function netTcpCloseWhileAccept() {
     const listener = Deno.listen({ port: 4501 });
     const p = listener.accept();
     listener.close();
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         await p;
       },
       Deno.errors.BadResource,
@@ -116,7 +116,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function netUnixCloseWhileAccept(): Promise<void> {
+  async function netUnixCloseWhileAccept() {
     const filePath = await Deno.makeTempFile();
     const listener = Deno.listen({
       path: filePath,
@@ -125,7 +125,7 @@ unitTest(
     const p = listener.accept();
     listener.close();
     await assertThrowsAsync(
-      async (): Promise<void> => {
+      async () => {
         await p;
       },
       Deno.errors.BadResource,
@@ -136,10 +136,10 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netTcpConcurrentAccept(): Promise<void> {
+  async function netTcpConcurrentAccept() {
     const listener = Deno.listen({ port: 4502 });
     let acceptErrCount = 0;
-    const checkErr = (e: Error): void => {
+    const checkErr = (e: Error) => {
       if (e.message === "Listener has been closed") {
         assertEquals(acceptErrCount, 1);
       } else if (e.message === "Another accept task is ongoing") {
@@ -160,11 +160,11 @@ unitTest(
 // TODO(jsouto): Enable when tokio updates mio to v0.7!
 unitTest(
   { ignore: true, perms: { read: true, write: true } },
-  async function netUnixConcurrentAccept(): Promise<void> {
+  async function netUnixConcurrentAccept() {
     const filePath = await Deno.makeTempFile();
     const listener = Deno.listen({ transport: "unix", path: filePath });
     let acceptErrCount = 0;
-    const checkErr = (e: Error): void => {
+    const checkErr = (e: Error) => {
       if (e.message === "Listener has been closed") {
         assertEquals(acceptErrCount, 1);
       } else if (e.message === "Another accept task is ongoing") {
@@ -182,12 +182,10 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, async function netTcpDialListen(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function netTcpDialListen() {
   const listener = Deno.listen({ port: 3500 });
   listener.accept().then(
-    async (conn): Promise<void> => {
+    async (conn) => {
       assert(conn.remoteAddr != null);
       assert(conn.localAddr.transport === "tcp");
       assertEquals(conn.localAddr.hostname, "127.0.0.1");
@@ -221,11 +219,11 @@ unitTest({ perms: { net: true } }, async function netTcpDialListen(): Promise<
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function netUnixDialListen(): Promise<void> {
+  async function netUnixDialListen() {
     const filePath = await Deno.makeTempFile();
     const listener = Deno.listen({ path: filePath, transport: "unix" });
     listener.accept().then(
-      async (conn): Promise<void> => {
+      async (conn) => {
         assert(conn.remoteAddr != null);
         assert(conn.localAddr.transport === "unix");
         assertEquals(conn.localAddr.path, filePath);
@@ -257,7 +255,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netUdpSendReceive(): Promise<void> {
+  async function netUdpSendReceive() {
     const alice = Deno.listenDatagram({ port: 3500, transport: "udp" });
     assert(alice.addr.transport === "udp");
     assertEquals(alice.addr.port, 3500);
@@ -287,7 +285,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netUdpConcurrentSendReceive(): Promise<void> {
+  async function netUdpConcurrentSendReceive() {
     const socket = Deno.listenDatagram({ port: 3500, transport: "udp" });
     assert(socket.addr.transport === "udp");
     assertEquals(socket.addr.port, 3500);
@@ -311,7 +309,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netUdpBorrowMutError(): Promise<void> {
+  async function netUdpBorrowMutError() {
     const socket = Deno.listenDatagram({
       port: 4501,
       transport: "udp",
@@ -326,7 +324,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function netUnixPacketSendReceive(): Promise<void> {
+  async function netUnixPacketSendReceive() {
     const filePath = await Deno.makeTempFile();
     const alice = Deno.listenDatagram({
       path: filePath,
@@ -361,7 +359,7 @@ unitTest(
 // TODO(piscisaureus): Enable after Tokio v0.3/v1.0 upgrade.
 unitTest(
   { ignore: true, perms: { read: true, write: true } },
-  async function netUnixPacketConcurrentSendReceive(): Promise<void> {
+  async function netUnixPacketConcurrentSendReceive() {
     const filePath = await Deno.makeTempFile();
     const socket = Deno.listenDatagram({
       path: filePath,
@@ -388,10 +386,10 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netTcpListenIteratorBreakClosesResource(): Promise<void> {
+  async function netTcpListenIteratorBreakClosesResource() {
     const promise = deferred();
 
-    async function iterate(listener: Deno.Listener): Promise<void> {
+    async function iterate(listener: Deno.Listener) {
       let i = 0;
 
       for await (const conn of listener) {
@@ -422,7 +420,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netTcpListenCloseWhileIterating(): Promise<void> {
+  async function netTcpListenCloseWhileIterating() {
     const listener = Deno.listen({ port: 8001 });
     const nextWhileClosing = listener[Symbol.asyncIterator]().next();
     listener.close();
@@ -435,7 +433,7 @@ unitTest(
 
 unitTest(
   { perms: { net: true } },
-  async function netUdpListenCloseWhileIterating(): Promise<void> {
+  async function netUdpListenCloseWhileIterating() {
     const socket = Deno.listenDatagram({ port: 8000, transport: "udp" });
     const nextWhileClosing = socket[Symbol.asyncIterator]().next();
     socket.close();
@@ -448,7 +446,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function netUnixListenCloseWhileIterating(): Promise<void> {
+  async function netUnixListenCloseWhileIterating() {
     const filePath = Deno.makeTempFileSync();
     const socket = Deno.listen({ path: filePath, transport: "unix" });
     const nextWhileClosing = socket[Symbol.asyncIterator]().next();
@@ -462,7 +460,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  async function netUnixPacketListenCloseWhileIterating(): Promise<void> {
+  async function netUnixPacketListenCloseWhileIterating() {
     const filePath = Deno.makeTempFileSync();
     const socket = Deno.listenDatagram({
       path: filePath,
@@ -483,10 +481,10 @@ unitTest(
     ignore: true,
     perms: { net: true },
   },
-  async function netListenAsyncIterator(): Promise<void> {
+  async function netListenAsyncIterator() {
     const addr = { hostname: "127.0.0.1", port: 3500 };
     const listener = Deno.listen(addr);
-    const runAsyncIterator = async (): Promise<void> => {
+    const runAsyncIterator = async () => {
       for await (const conn of listener) {
         await conn.write(new Uint8Array([1, 2, 3]));
         conn.close();
@@ -552,7 +550,7 @@ unitTest(
   async function netHangsOnClose() {
     let acceptedConn: Deno.Conn;
 
-    async function iteratorReq(listener: Deno.Listener): Promise<void> {
+    async function iteratorReq(listener: Deno.Listener) {
       const p = new Uint8Array(10);
       const conn = await listener.accept();
       acceptedConn = conn;
diff --git a/cli/tests/unit/opcall_test.ts b/cli/tests/unit/opcall_test.ts
index bd549570e..9c0d39d2e 100644
--- a/cli/tests/unit/opcall_test.ts
+++ b/cli/tests/unit/opcall_test.ts
@@ -21,7 +21,7 @@ declare global {
   }
 }
 
-unitTest(async function opsAsyncBadResource(): Promise<void> {
+unitTest(async function opsAsyncBadResource() {
   try {
     const nonExistingRid = 9999;
     await Deno.core.opAsync(
@@ -36,7 +36,7 @@ unitTest(async function opsAsyncBadResource(): Promise<void> {
   }
 });
 
-unitTest(function opsSyncBadResource(): void {
+unitTest(function opsSyncBadResource() {
   try {
     const nonExistingRid = 9999;
     Deno.core.opSync("op_read_sync", nonExistingRid, new Uint8Array(0));
diff --git a/cli/tests/unit/os_test.ts b/cli/tests/unit/os_test.ts
index daa7a1ca2..d7fb88882 100644
--- a/cli/tests/unit/os_test.ts
+++ b/cli/tests/unit/os_test.ts
@@ -7,7 +7,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { env: true } }, function envSuccess(): void {
+unitTest({ perms: { env: true } }, function envSuccess() {
   Deno.env.set("TEST_VAR", "A");
   const env = Deno.env.toObject();
   Deno.env.set("TEST_VAR", "B");
@@ -15,19 +15,19 @@ unitTest({ perms: { env: true } }, function envSuccess(): void {
   assertNotEquals(Deno.env.get("TEST_VAR"), env["TEST_VAR"]);
 });
 
-unitTest({ perms: { env: true } }, function envNotFound(): void {
+unitTest({ perms: { env: true } }, function envNotFound() {
   const r = Deno.env.get("env_var_does_not_exist!");
   assertEquals(r, undefined);
 });
 
-unitTest({ perms: { env: true } }, function deleteEnv(): void {
+unitTest({ perms: { env: true } }, function deleteEnv() {
   Deno.env.set("TEST_VAR", "A");
   assertEquals(Deno.env.get("TEST_VAR"), "A");
   assertEquals(Deno.env.delete("TEST_VAR"), undefined);
   assertEquals(Deno.env.get("TEST_VAR"), undefined);
 });
 
-unitTest({ perms: { env: true } }, function avoidEmptyNamedEnv(): void {
+unitTest({ perms: { env: true } }, function avoidEmptyNamedEnv() {
   assertThrows(() => Deno.env.set("", "v"), TypeError);
   assertThrows(() => Deno.env.set("a=a", "v"), TypeError);
   assertThrows(() => Deno.env.set("a\0a", "v"), TypeError);
@@ -42,13 +42,13 @@ unitTest({ perms: { env: true } }, function avoidEmptyNamedEnv(): void {
   assertThrows(() => Deno.env.delete("a\0a"), TypeError);
 });
 
-unitTest(function envPermissionDenied1(): void {
+unitTest(function envPermissionDenied1() {
   assertThrows(() => {
     Deno.env.toObject();
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest(function envPermissionDenied2(): void {
+unitTest(function envPermissionDenied2() {
   assertThrows(() => {
     Deno.env.get("PATH");
   }, Deno.errors.PermissionDenied);
@@ -70,7 +70,7 @@ unitTest(
     const checkChildEnv = async (
       inputEnv: Record<string, string>,
       expectedEnv: Record<string, string>,
-    ): Promise<void> => {
+    ) => {
       const src = `
       console.log(
         ${JSON.stringify(Object.keys(expectedEnv))}.map(k => Deno.env.get(k))
@@ -122,17 +122,17 @@ unitTest(
   },
 );
 
-unitTest(function osPid(): void {
+unitTest(function osPid() {
   assert(Deno.pid > 0);
 });
 
-unitTest(function osPpid(): void {
+unitTest(function osPpid() {
   assert(Deno.ppid > 0);
 });
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function osPpidIsEqualToPidOfParentProcess(): Promise<void> {
+  async function osPpidIsEqualToPidOfParentProcess() {
     const decoder = new TextDecoder();
     const process = Deno.run({
       cmd: [Deno.execPath(), "eval", "-p", "--unstable", "Deno.ppid"],
@@ -148,11 +148,11 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: true } }, function execPath(): void {
+unitTest({ perms: { read: true } }, function execPath() {
   assertNotEquals(Deno.execPath(), "");
 });
 
-unitTest({ perms: { read: false } }, function execPathPerm(): void {
+unitTest({ perms: { read: false } }, function execPathPerm() {
   assertThrows(
     () => {
       Deno.execPath();
@@ -162,38 +162,38 @@ unitTest({ perms: { read: false } }, function execPathPerm(): void {
   );
 });
 
-unitTest({ perms: { env: true } }, function loadavgSuccess(): void {
+unitTest({ perms: { env: true } }, function loadavgSuccess() {
   const load = Deno.loadavg();
   assertEquals(load.length, 3);
 });
 
-unitTest({ perms: { env: false } }, function loadavgPerm(): void {
+unitTest({ perms: { env: false } }, function loadavgPerm() {
   assertThrows(() => {
     Deno.loadavg();
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { env: true } }, function hostnameDir(): void {
+unitTest({ perms: { env: true } }, function hostnameDir() {
   assertNotEquals(Deno.hostname(), "");
 });
 
-unitTest({ perms: { env: false } }, function hostnamePerm(): void {
+unitTest({ perms: { env: false } }, function hostnamePerm() {
   assertThrows(() => {
     Deno.hostname();
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { env: true } }, function releaseDir(): void {
+unitTest({ perms: { env: true } }, function releaseDir() {
   assertNotEquals(Deno.osRelease(), "");
 });
 
-unitTest({ perms: { env: false } }, function releasePerm(): void {
+unitTest({ perms: { env: false } }, function releasePerm() {
   assertThrows(() => {
     Deno.osRelease();
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { env: true } }, function systemMemoryInfo(): void {
+unitTest({ perms: { env: true } }, function systemMemoryInfo() {
   const info = Deno.systemMemoryInfo();
   assert(info.total >= 0);
   assert(info.free >= 0);
diff --git a/cli/tests/unit/path_from_url_test.ts b/cli/tests/unit/path_from_url_test.ts
index d086ce1dc..887b42366 100644
--- a/cli/tests/unit/path_from_url_test.ts
+++ b/cli/tests/unit/path_from_url_test.ts
@@ -5,7 +5,7 @@ const { pathFromURL } = Deno[Deno.internal];
 
 unitTest(
   { ignore: Deno.build.os === "windows" },
-  function pathFromURLPosix(): void {
+  function pathFromURLPosix() {
     assertEquals(
       pathFromURL(new URL("file:///test/directory")),
       "/test/directory",
@@ -17,7 +17,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os !== "windows" },
-  function pathFromURLWin32(): void {
+  function pathFromURLWin32() {
     assertEquals(
       pathFromURL(new URL("file:///c:/windows/test")),
       "c:\\windows\\test",
diff --git a/cli/tests/unit/performance_test.ts b/cli/tests/unit/performance_test.ts
index 94af0731c..989d221d8 100644
--- a/cli/tests/unit/performance_test.ts
+++ b/cli/tests/unit/performance_test.ts
@@ -8,12 +8,10 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { hrtime: false } }, async function performanceNow(): Promise<
-  void
-> {
+unitTest({ perms: { hrtime: false } }, async function performanceNow() {
   const resolvable = deferred();
   const start = performance.now();
-  setTimeout((): void => {
+  setTimeout(() => {
     const end = performance.now();
     assert(end - start >= 10);
     resolvable.resolve();
@@ -82,7 +80,7 @@ unitTest(function performanceMeasure() {
   });
 });
 
-unitTest(function performanceCustomInspectFunction(): void {
+unitTest(function performanceCustomInspectFunction() {
   assertStringIncludes(Deno.inspect(performance), "Performance");
   assertStringIncludes(
     Deno.inspect(Performance.prototype),
@@ -90,7 +88,7 @@ unitTest(function performanceCustomInspectFunction(): void {
   );
 });
 
-unitTest(function performanceMarkCustomInspectFunction(): void {
+unitTest(function performanceMarkCustomInspectFunction() {
   const mark1 = performance.mark("mark1");
   assertStringIncludes(Deno.inspect(mark1), "PerformanceMark");
   assertStringIncludes(
@@ -99,7 +97,7 @@ unitTest(function performanceMarkCustomInspectFunction(): void {
   );
 });
 
-unitTest(function performanceMeasureCustomInspectFunction(): void {
+unitTest(function performanceMeasureCustomInspectFunction() {
   const measure1 = performance.measure("measure1");
   assertStringIncludes(Deno.inspect(measure1), "PerformanceMeasure");
   assertStringIncludes(
diff --git a/cli/tests/unit/permissions_test.ts b/cli/tests/unit/permissions_test.ts
index 8a6d7e9aa..d89b1e355 100644
--- a/cli/tests/unit/permissions_test.ts
+++ b/cli/tests/unit/permissions_test.ts
@@ -7,14 +7,14 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest(async function permissionInvalidName(): Promise<void> {
+unitTest(async function permissionInvalidName() {
   await assertThrowsAsync(async () => {
     // deno-lint-ignore no-explicit-any
     await Deno.permissions.query({ name: "foo" as any });
   }, TypeError);
 });
 
-unitTest(async function permissionNetInvalidHost(): Promise<void> {
+unitTest(async function permissionNetInvalidHost() {
   await assertThrowsAsync(async () => {
     await Deno.permissions.query({ name: "net", host: ":" });
   }, URIError);
diff --git a/cli/tests/unit/process_test.ts b/cli/tests/unit/process_test.ts
index f187efe71..2d0a15b16 100644
--- a/cli/tests/unit/process_test.ts
+++ b/cli/tests/unit/process_test.ts
@@ -7,7 +7,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { read: true } }, function runPermissions(): void {
+unitTest({ perms: { read: true } }, function runPermissions() {
   assertThrows(() => {
     Deno.run({ cmd: [Deno.execPath(), "eval", "console.log('hello world')"] });
   }, Deno.errors.PermissionDenied);
@@ -15,7 +15,7 @@ unitTest({ perms: { read: true } }, function runPermissions(): void {
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runSuccess(): Promise<void> {
+  async function runSuccess() {
     const p = Deno.run({
       cmd: [Deno.execPath(), "eval", "console.log('hello world')"],
       stdout: "piped",
@@ -32,7 +32,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runUrl(): Promise<void> {
+  async function runUrl() {
     const p = Deno.run({
       cmd: [
         new URL(`file:///${Deno.execPath()}`),
@@ -73,7 +73,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  function runInvalidStdio(): void {
+  function runInvalidStdio() {
     assertThrows(() =>
       Deno.run({
         cmd: [Deno.execPath(), "eval", "console.log('hello world')"],
@@ -100,7 +100,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runCommandFailedWithCode(): Promise<void> {
+  async function runCommandFailedWithCode() {
     const p = Deno.run({
       cmd: [Deno.execPath(), "eval", "Deno.exit(41 + 1)"],
     });
@@ -118,7 +118,7 @@ unitTest(
     ignore: Deno.build.os === "windows",
     perms: { run: true, read: true },
   },
-  async function runCommandFailedWithSignal(): Promise<void> {
+  async function runCommandFailedWithSignal() {
     const p = Deno.run({
       cmd: [Deno.execPath(), "eval", "--unstable", "Deno.kill(Deno.pid, 9)"],
     });
@@ -130,7 +130,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { run: true } }, function runNotFound(): void {
+unitTest({ perms: { run: true } }, function runNotFound() {
   let error;
   try {
     Deno.run({ cmd: ["this file hopefully doesn't exist"] });
@@ -143,7 +143,7 @@ unitTest({ perms: { run: true } }, function runNotFound(): void {
 
 unitTest(
   { perms: { write: true, run: true, read: true } },
-  async function runWithCwdIsAsync(): Promise<void> {
+  async function runWithCwdIsAsync() {
     const enc = new TextEncoder();
     const cwd = await Deno.makeTempDir({ prefix: "deno_command_test" });
 
@@ -287,7 +287,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runOutput(): Promise<void> {
+  async function runOutput() {
     const p = Deno.run({
       cmd: [
         Deno.execPath(),
@@ -325,7 +325,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true, read: true } },
-  async function runRedirectStdoutStderr(): Promise<void> {
+  async function runRedirectStdoutStderr() {
     const tempDir = await Deno.makeTempDir();
     const fileName = tempDir + "/redirected_stdio.txt";
     const file = await Deno.open(fileName, {
@@ -358,7 +358,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, write: true, read: true } },
-  async function runRedirectStdin(): Promise<void> {
+  async function runRedirectStdin() {
     const tempDir = await Deno.makeTempDir();
     const fileName = tempDir + "/redirected_stdio.txt";
     const encoder = new TextEncoder();
@@ -383,7 +383,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runEnv(): Promise<void> {
+  async function runEnv() {
     const p = Deno.run({
       cmd: [
         Deno.execPath(),
@@ -405,7 +405,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runClose(): Promise<void> {
+  async function runClose() {
     const p = Deno.run({
       cmd: [
         Deno.execPath(),
@@ -428,7 +428,7 @@ unitTest(
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function runKillAfterStatus(): Promise<void> {
+  async function runKillAfterStatus() {
     const p = Deno.run({
       cmd: [Deno.execPath(), "eval", 'console.log("hello")'],
     });
@@ -454,7 +454,7 @@ unitTest(
   },
 );
 
-unitTest(function signalNumbers(): void {
+unitTest(function signalNumbers() {
   if (Deno.build.os === "darwin") {
     assertEquals(Deno.Signal.SIGSTOP, 17);
   } else if (Deno.build.os === "linux") {
@@ -462,7 +462,7 @@ unitTest(function signalNumbers(): void {
   }
 });
 
-unitTest(function killPermissions(): void {
+unitTest(function killPermissions() {
   assertThrows(() => {
     // Unlike the other test cases, we don't have permission to spawn a
     // subprocess we can safely kill. Instead we send SIGCONT to the current
@@ -474,7 +474,7 @@ unitTest(function killPermissions(): void {
 
 unitTest(
   { perms: { run: true, read: true } },
-  async function killSuccess(): Promise<void> {
+  async function killSuccess() {
     const p = Deno.run({
       cmd: [Deno.execPath(), "eval", "setTimeout(() => {}, 10000)"],
     });
@@ -497,7 +497,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { run: true, read: true } }, function killFailed(): void {
+unitTest({ perms: { run: true, read: true } }, function killFailed() {
   const p = Deno.run({
     cmd: [Deno.execPath(), "eval", "setTimeout(() => {}, 10000)"],
   });
diff --git a/cli/tests/unit/progressevent_test.ts b/cli/tests/unit/progressevent_test.ts
index 6f165de2c..4d6b4c08f 100644
--- a/cli/tests/unit/progressevent_test.ts
+++ b/cli/tests/unit/progressevent_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertEquals, unitTest } from "./test_util.ts";
 
-unitTest(function progressEventConstruct(): void {
+unitTest(function progressEventConstruct() {
   const progressEventDefs = new ProgressEvent("progressEventType", {});
   assertEquals(progressEventDefs.lengthComputable, false);
   assertEquals(progressEventDefs.loaded, 0);
diff --git a/cli/tests/unit/read_dir_test.ts b/cli/tests/unit/read_dir_test.ts
index 829f7bfa2..2e4370153 100644
--- a/cli/tests/unit/read_dir_test.ts
+++ b/cli/tests/unit/read_dir_test.ts
@@ -8,7 +8,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-function assertSameContent(files: Deno.DirEntry[]): void {
+function assertSameContent(files: Deno.DirEntry[]) {
   let counter = 0;
 
   for (const entry of files) {
@@ -21,37 +21,35 @@ function assertSameContent(files: Deno.DirEntry[]): void {
   assertEquals(counter, 1);
 }
 
-unitTest({ perms: { read: true } }, function readDirSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function readDirSyncSuccess() {
   const files = [...Deno.readDirSync("cli/tests/")];
   assertSameContent(files);
 });
 
-unitTest({ perms: { read: true } }, function readDirSyncWithUrl(): void {
+unitTest({ perms: { read: true } }, function readDirSyncWithUrl() {
   const files = [...Deno.readDirSync(pathToAbsoluteFileUrl("cli/tests"))];
   assertSameContent(files);
 });
 
-unitTest({ perms: { read: false } }, function readDirSyncPerm(): void {
+unitTest({ perms: { read: false } }, function readDirSyncPerm() {
   assertThrows(() => {
     Deno.readDirSync("tests/");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function readDirSyncNotDir(): void {
+unitTest({ perms: { read: true } }, function readDirSyncNotDir() {
   assertThrows(() => {
     Deno.readDirSync("cli/tests/fixture.json");
   }, Error);
 });
 
-unitTest({ perms: { read: true } }, function readDirSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function readDirSyncNotFound() {
   assertThrows(() => {
     Deno.readDirSync("bad_dir_name");
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { read: true } }, async function readDirSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function readDirSuccess() {
   const files = [];
   for await (const dirEntry of Deno.readDir("cli/tests/")) {
     files.push(dirEntry);
@@ -59,9 +57,7 @@ unitTest({ perms: { read: true } }, async function readDirSuccess(): Promise<
   assertSameContent(files);
 });
 
-unitTest({ perms: { read: true } }, async function readDirWithUrl(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function readDirWithUrl() {
   const files = [];
   for await (
     const dirEntry of Deno.readDir(pathToAbsoluteFileUrl("cli/tests"))
@@ -71,9 +67,7 @@ unitTest({ perms: { read: true } }, async function readDirWithUrl(): Promise<
   assertSameContent(files);
 });
 
-unitTest({ perms: { read: false } }, async function readDirPerm(): Promise<
-  void
-> {
+unitTest({ perms: { read: false } }, async function readDirPerm() {
   await assertThrowsAsync(async () => {
     await Deno.readDir("tests/")[Symbol.asyncIterator]().next();
   }, Deno.errors.PermissionDenied);
@@ -92,7 +86,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true }, ignore: Deno.build.os == "windows" },
-  function readDirDevFdSync(): void {
+  function readDirDevFdSync() {
     for (const _ of Deno.readDirSync("/dev/fd")) {
       // We don't actually care whats in here; just that we don't panic on non regular file entries
     }
diff --git a/cli/tests/unit/read_file_test.ts b/cli/tests/unit/read_file_test.ts
index d8d1cddf2..f638c7a7c 100644
--- a/cli/tests/unit/read_file_test.ts
+++ b/cli/tests/unit/read_file_test.ts
@@ -8,7 +8,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { read: true } }, function readFileSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function readFileSyncSuccess() {
   const data = Deno.readFileSync("cli/tests/fixture.json");
   assert(data.byteLength > 0);
   const decoder = new TextDecoder("utf-8");
@@ -17,7 +17,7 @@ unitTest({ perms: { read: true } }, function readFileSyncSuccess(): void {
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: true } }, function readFileSyncUrl(): void {
+unitTest({ perms: { read: true } }, function readFileSyncUrl() {
   const data = Deno.readFileSync(
     pathToAbsoluteFileUrl("cli/tests/fixture.json"),
   );
@@ -28,21 +28,19 @@ unitTest({ perms: { read: true } }, function readFileSyncUrl(): void {
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: false } }, function readFileSyncPerm(): void {
+unitTest({ perms: { read: false } }, function readFileSyncPerm() {
   assertThrows(() => {
     Deno.readFileSync("cli/tests/fixture.json");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function readFileSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function readFileSyncNotFound() {
   assertThrows(() => {
     Deno.readFileSync("bad_filename");
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { read: true } }, async function readFileUrl(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function readFileUrl() {
   const data = await Deno.readFile(
     pathToAbsoluteFileUrl("cli/tests/fixture.json"),
   );
@@ -53,9 +51,7 @@ unitTest({ perms: { read: true } }, async function readFileUrl(): Promise<
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: true } }, async function readFileSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function readFileSuccess() {
   const data = await Deno.readFile("cli/tests/fixture.json");
   assert(data.byteLength > 0);
   const decoder = new TextDecoder("utf-8");
@@ -64,15 +60,13 @@ unitTest({ perms: { read: true } }, async function readFileSuccess(): Promise<
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: false } }, async function readFilePerm(): Promise<
-  void
-> {
+unitTest({ perms: { read: false } }, async function readFilePerm() {
   await assertThrowsAsync(async () => {
     await Deno.readFile("cli/tests/fixture.json");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function readFileSyncLoop(): void {
+unitTest({ perms: { read: true } }, function readFileSyncLoop() {
   for (let i = 0; i < 256; i++) {
     Deno.readFileSync("cli/tests/fixture.json");
   }
@@ -80,7 +74,7 @@ unitTest({ perms: { read: true } }, function readFileSyncLoop(): void {
 
 unitTest(
   { perms: { read: true } },
-  async function readFileDoesNotLeakResources(): Promise<void> {
+  async function readFileDoesNotLeakResources() {
     const resourcesBefore = Deno.resources();
     await assertThrowsAsync(async () => await Deno.readFile("cli"));
     assertEquals(resourcesBefore, Deno.resources());
@@ -89,7 +83,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true } },
-  function readFileSyncDoesNotLeakResources(): void {
+  function readFileSyncDoesNotLeakResources() {
     const resourcesBefore = Deno.resources();
     assertThrows(() => Deno.readFileSync("cli"));
     assertEquals(resourcesBefore, Deno.resources());
@@ -98,7 +92,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true } },
-  async function readFileWithAbortSignal(): Promise<void> {
+  async function readFileWithAbortSignal() {
     const ac = new AbortController();
     queueMicrotask(() => ac.abort());
     await assertThrowsAsync(async () => {
@@ -109,7 +103,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true } },
-  async function readTextileWithAbortSignal(): Promise<void> {
+  async function readTextileWithAbortSignal() {
     const ac = new AbortController();
     queueMicrotask(() => ac.abort());
     await assertThrowsAsync(async () => {
diff --git a/cli/tests/unit/read_link_test.ts b/cli/tests/unit/read_link_test.ts
index cab27cbdc..3d00cda1a 100644
--- a/cli/tests/unit/read_link_test.ts
+++ b/cli/tests/unit/read_link_test.ts
@@ -9,7 +9,7 @@ import {
 
 unitTest(
   { perms: { write: true, read: true } },
-  function readLinkSyncSuccess(): void {
+  function readLinkSyncSuccess() {
     const testDir = Deno.makeTempDirSync();
     const target = testDir +
       (Deno.build.os == "windows" ? "\\target" : "/target");
@@ -24,7 +24,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  function readLinkSyncUrlSuccess(): void {
+  function readLinkSyncUrlSuccess() {
     const testDir = Deno.makeTempDirSync();
     const target = testDir +
       (Deno.build.os == "windows" ? "\\target" : "/target");
@@ -37,13 +37,13 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: false } }, function readLinkSyncPerm(): void {
+unitTest({ perms: { read: false } }, function readLinkSyncPerm() {
   assertThrows(() => {
     Deno.readLinkSync("/symlink");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function readLinkSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function readLinkSyncNotFound() {
   assertThrows(() => {
     Deno.readLinkSync("bad_filename");
   }, Deno.errors.NotFound);
@@ -51,7 +51,7 @@ unitTest({ perms: { read: true } }, function readLinkSyncNotFound(): void {
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function readLinkSuccess(): Promise<void> {
+  async function readLinkSuccess() {
     const testDir = Deno.makeTempDirSync();
     const target = testDir +
       (Deno.build.os == "windows" ? "\\target" : "/target");
@@ -66,7 +66,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function readLinkUrlSuccess(): Promise<void> {
+  async function readLinkUrlSuccess() {
     const testDir = Deno.makeTempDirSync();
     const target = testDir +
       (Deno.build.os == "windows" ? "\\target" : "/target");
@@ -79,9 +79,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: false } }, async function readLinkPerm(): Promise<
-  void
-> {
+unitTest({ perms: { read: false } }, async function readLinkPerm() {
   await assertThrowsAsync(async () => {
     await Deno.readLink("/symlink");
   }, Deno.errors.PermissionDenied);
diff --git a/cli/tests/unit/read_text_file_test.ts b/cli/tests/unit/read_text_file_test.ts
index 2223d9c18..a7eb1a730 100644
--- a/cli/tests/unit/read_text_file_test.ts
+++ b/cli/tests/unit/read_text_file_test.ts
@@ -7,14 +7,14 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { read: true } }, function readTextFileSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function readTextFileSyncSuccess() {
   const data = Deno.readTextFileSync("cli/tests/fixture.json");
   assert(data.length > 0);
   const pkg = JSON.parse(data);
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: true } }, function readTextFileSyncByUrl(): void {
+unitTest({ perms: { read: true } }, function readTextFileSyncByUrl() {
   const data = Deno.readTextFileSync(
     pathToAbsoluteFileUrl("cli/tests/fixture.json"),
   );
@@ -23,13 +23,13 @@ unitTest({ perms: { read: true } }, function readTextFileSyncByUrl(): void {
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: false } }, function readTextFileSyncPerm(): void {
+unitTest({ perms: { read: false } }, function readTextFileSyncPerm() {
   assertThrows(() => {
     Deno.readTextFileSync("cli/tests/fixture.json");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function readTextFileSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function readTextFileSyncNotFound() {
   assertThrows(() => {
     Deno.readTextFileSync("bad_filename");
   }, Deno.errors.NotFound);
@@ -37,7 +37,7 @@ unitTest({ perms: { read: true } }, function readTextFileSyncNotFound(): void {
 
 unitTest(
   { perms: { read: true } },
-  async function readTextFileSuccess(): Promise<void> {
+  async function readTextFileSuccess() {
     const data = await Deno.readTextFile("cli/tests/fixture.json");
     assert(data.length > 0);
     const pkg = JSON.parse(data);
@@ -45,9 +45,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: true } }, async function readTextFileByUrl(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function readTextFileByUrl() {
   const data = await Deno.readTextFile(
     pathToAbsoluteFileUrl("cli/tests/fixture.json"),
   );
@@ -56,15 +54,13 @@ unitTest({ perms: { read: true } }, async function readTextFileByUrl(): Promise<
   assertEquals(pkg.name, "deno");
 });
 
-unitTest({ perms: { read: false } }, async function readTextFilePerm(): Promise<
-  void
-> {
+unitTest({ perms: { read: false } }, async function readTextFilePerm() {
   await assertThrowsAsync(async () => {
     await Deno.readTextFile("cli/tests/fixture.json");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function readTextFileSyncLoop(): void {
+unitTest({ perms: { read: true } }, function readTextFileSyncLoop() {
   for (let i = 0; i < 256; i++) {
     Deno.readTextFileSync("cli/tests/fixture.json");
   }
@@ -72,7 +68,7 @@ unitTest({ perms: { read: true } }, function readTextFileSyncLoop(): void {
 
 unitTest(
   { perms: { read: true } },
-  async function readTextFileDoesNotLeakResources(): Promise<void> {
+  async function readTextFileDoesNotLeakResources() {
     const resourcesBefore = Deno.resources();
     await assertThrowsAsync(async () => await Deno.readTextFile("cli"));
     assertEquals(resourcesBefore, Deno.resources());
@@ -81,7 +77,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true } },
-  function readTextFileSyncDoesNotLeakResources(): void {
+  function readTextFileSyncDoesNotLeakResources() {
     const resourcesBefore = Deno.resources();
     assertThrows(() => Deno.readTextFileSync("cli"));
     assertEquals(resourcesBefore, Deno.resources());
diff --git a/cli/tests/unit/real_path_test.ts b/cli/tests/unit/real_path_test.ts
index 10e060578..b84b0c0df 100644
--- a/cli/tests/unit/real_path_test.ts
+++ b/cli/tests/unit/real_path_test.ts
@@ -9,7 +9,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { read: true } }, function realPathSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function realPathSyncSuccess() {
   const relative = "cli/tests/fixture.json";
   const realPath = Deno.realPathSync(relative);
   if (Deno.build.os !== "windows") {
@@ -21,7 +21,7 @@ unitTest({ perms: { read: true } }, function realPathSyncSuccess(): void {
   }
 });
 
-unitTest({ perms: { read: true } }, function realPathSyncUrl(): void {
+unitTest({ perms: { read: true } }, function realPathSyncUrl() {
   const relative = "cli/tests/fixture.json";
   const url = pathToAbsoluteFileUrl(relative);
   assertEquals(Deno.realPathSync(relative), Deno.realPathSync(url));
@@ -31,7 +31,7 @@ unitTest(
   {
     perms: { read: true, write: true },
   },
-  function realPathSyncSymlink(): void {
+  function realPathSyncSymlink() {
     const testDir = Deno.makeTempDirSync();
     const target = testDir + "/target";
     const symlink = testDir + "/symln";
@@ -48,21 +48,19 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: false } }, function realPathSyncPerm(): void {
+unitTest({ perms: { read: false } }, function realPathSyncPerm() {
   assertThrows(() => {
     Deno.realPathSync("some_file");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function realPathSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function realPathSyncNotFound() {
   assertThrows(() => {
     Deno.realPathSync("bad_filename");
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { read: true } }, async function realPathSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function realPathSuccess() {
   const relativePath = "cli/tests/fixture.json";
   const realPath = await Deno.realPath(relativePath);
   if (Deno.build.os !== "windows") {
@@ -76,7 +74,7 @@ unitTest({ perms: { read: true } }, async function realPathSuccess(): Promise<
 
 unitTest(
   { perms: { read: true } },
-  async function realPathUrl(): Promise<void> {
+  async function realPathUrl() {
     const relative = "cli/tests/fixture.json";
     const url = pathToAbsoluteFileUrl(relative);
     assertEquals(await Deno.realPath(relative), await Deno.realPath(url));
@@ -87,7 +85,7 @@ unitTest(
   {
     perms: { read: true, write: true },
   },
-  async function realPathSymlink(): Promise<void> {
+  async function realPathSymlink() {
     const testDir = Deno.makeTempDirSync();
     const target = testDir + "/target";
     const symlink = testDir + "/symln";
@@ -104,17 +102,13 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: false } }, async function realPathPerm(): Promise<
-  void
-> {
+unitTest({ perms: { read: false } }, async function realPathPerm() {
   await assertThrowsAsync(async () => {
     await Deno.realPath("some_file");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, async function realPathNotFound(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function realPathNotFound() {
   await assertThrowsAsync(async () => {
     await Deno.realPath("bad_filename");
   }, Deno.errors.NotFound);
diff --git a/cli/tests/unit/remove_test.ts b/cli/tests/unit/remove_test.ts
index 087cc3a73..5f39b1c79 100644
--- a/cli/tests/unit/remove_test.ts
+++ b/cli/tests/unit/remove_test.ts
@@ -10,7 +10,7 @@ const REMOVE_METHODS = ["remove", "removeSync"] as const;
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeDirSuccess(): Promise<void> {
+  async function removeDirSuccess() {
     for (const method of REMOVE_METHODS) {
       // REMOVE EMPTY DIRECTORY
       const path = Deno.makeTempDirSync() + "/subdir";
@@ -28,7 +28,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeFileSuccess(): Promise<void> {
+  async function removeFileSuccess() {
     for (const method of REMOVE_METHODS) {
       // REMOVE FILE
       const enc = new TextEncoder();
@@ -48,7 +48,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeFileByUrl(): Promise<void> {
+  async function removeFileByUrl() {
     for (const method of REMOVE_METHODS) {
       // REMOVE FILE
       const enc = new TextEncoder();
@@ -73,7 +73,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeFail(): Promise<void> {
+  async function removeFail() {
     for (const method of REMOVE_METHODS) {
       // NON-EMPTY DIRECTORY
       const path = Deno.makeTempDirSync() + "/dir/subdir";
@@ -100,7 +100,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeDanglingSymlinkSuccess(): Promise<void> {
+  async function removeDanglingSymlinkSuccess() {
     for (const method of REMOVE_METHODS) {
       const danglingSymlinkPath = Deno.makeTempDirSync() + "/dangling_symlink";
       if (Deno.build.os === "windows") {
@@ -122,7 +122,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeValidSymlinkSuccess(): Promise<void> {
+  async function removeValidSymlinkSuccess() {
     for (const method of REMOVE_METHODS) {
       const encoder = new TextEncoder();
       const data = encoder.encode("Test");
@@ -146,9 +146,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: false } }, async function removePerm(): Promise<
-  void
-> {
+unitTest({ perms: { write: false } }, async function removePerm() {
   for (const method of REMOVE_METHODS) {
     await assertThrowsAsync(async () => {
       await Deno[method]("/baddir");
@@ -158,7 +156,7 @@ unitTest({ perms: { write: false } }, async function removePerm(): Promise<
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeAllDirSuccess(): Promise<void> {
+  async function removeAllDirSuccess() {
     for (const method of REMOVE_METHODS) {
       // REMOVE EMPTY DIRECTORY
       let path = Deno.makeTempDirSync() + "/dir/subdir";
@@ -195,7 +193,7 @@ unitTest(
 
 unitTest(
   { perms: { write: true, read: true } },
-  async function removeAllFileSuccess(): Promise<void> {
+  async function removeAllFileSuccess() {
     for (const method of REMOVE_METHODS) {
       // REMOVE FILE
       const enc = new TextEncoder();
@@ -214,9 +212,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: true } }, async function removeAllFail(): Promise<
-  void
-> {
+unitTest({ perms: { write: true } }, async function removeAllFail() {
   for (const method of REMOVE_METHODS) {
     // NON-EXISTENT DIRECTORY/FILE
     await assertThrowsAsync(async () => {
@@ -226,9 +222,7 @@ unitTest({ perms: { write: true } }, async function removeAllFail(): Promise<
   }
 });
 
-unitTest({ perms: { write: false } }, async function removeAllPerm(): Promise<
-  void
-> {
+unitTest({ perms: { write: false } }, async function removeAllPerm() {
   for (const method of REMOVE_METHODS) {
     await assertThrowsAsync(async () => {
       await Deno[method]("/baddir", { recursive: true });
@@ -241,7 +235,7 @@ unitTest(
     ignore: Deno.build.os === "windows",
     perms: { write: true, read: true },
   },
-  async function removeUnixSocketSuccess(): Promise<void> {
+  async function removeUnixSocketSuccess() {
     for (const method of REMOVE_METHODS) {
       // MAKE TEMPORARY UNIX SOCKET
       const path = Deno.makeTempDirSync() + "/test.sock";
@@ -260,7 +254,7 @@ unitTest(
 if (Deno.build.os === "windows") {
   unitTest(
     { perms: { run: true, write: true, read: true } },
-    async function removeFileSymlink(): Promise<void> {
+    async function removeFileSymlink() {
       const symlink = Deno.run({
         cmd: ["cmd", "/c", "mklink", "file_link", "bar"],
         stdout: "null",
@@ -277,7 +271,7 @@ if (Deno.build.os === "windows") {
 
   unitTest(
     { perms: { run: true, write: true, read: true } },
-    async function removeDirSymlink(): Promise<void> {
+    async function removeDirSymlink() {
       const symlink = Deno.run({
         cmd: ["cmd", "/c", "mklink", "/d", "dir_link", "bar"],
         stdout: "null",
diff --git a/cli/tests/unit/rename_test.ts b/cli/tests/unit/rename_test.ts
index 711b63aa7..c5df8e4a4 100644
--- a/cli/tests/unit/rename_test.ts
+++ b/cli/tests/unit/rename_test.ts
@@ -7,7 +7,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-function assertMissing(path: string): void {
+function assertMissing(path: string) {
   let caughtErr = false;
   let info;
   try {
@@ -20,12 +20,12 @@ function assertMissing(path: string): void {
   assertEquals(info, undefined);
 }
 
-function assertFile(path: string): void {
+function assertFile(path: string) {
   const info = Deno.lstatSync(path);
   assert(info.isFile);
 }
 
-function assertDirectory(path: string, mode?: number): void {
+function assertDirectory(path: string, mode?: number) {
   const info = Deno.lstatSync(path);
   assert(info.isDirectory);
   if (Deno.build.os !== "windows" && mode !== undefined) {
@@ -35,7 +35,7 @@ function assertDirectory(path: string, mode?: number): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function renameSyncSuccess(): void {
+  function renameSyncSuccess() {
     const testDir = Deno.makeTempDirSync();
     const oldpath = testDir + "/oldpath";
     const newpath = testDir + "/newpath";
@@ -48,7 +48,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function renameSyncWithURL(): void {
+  function renameSyncWithURL() {
     const testDir = Deno.makeTempDirSync();
     const oldpath = testDir + "/oldpath";
     const newpath = testDir + "/newpath";
@@ -64,7 +64,7 @@ unitTest(
 
 unitTest(
   { perms: { read: false, write: true } },
-  function renameSyncReadPerm(): void {
+  function renameSyncReadPerm() {
     assertThrows(() => {
       const oldpath = "/oldbaddir";
       const newpath = "/newbaddir";
@@ -75,7 +75,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: false } },
-  function renameSyncWritePerm(): void {
+  function renameSyncWritePerm() {
     assertThrows(() => {
       const oldpath = "/oldbaddir";
       const newpath = "/newbaddir";
@@ -86,7 +86,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function renameSuccess(): Promise<void> {
+  async function renameSuccess() {
     const testDir = Deno.makeTempDirSync();
     const oldpath = testDir + "/oldpath";
     const newpath = testDir + "/newpath";
@@ -99,7 +99,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function renameWithURL(): Promise<void> {
+  async function renameWithURL() {
     const testDir = Deno.makeTempDirSync();
     const oldpath = testDir + "/oldpath";
     const newpath = testDir + "/newpath";
@@ -119,7 +119,7 @@ function readFileString(filename: string): string {
   return dec.decode(dataRead);
 }
 
-function writeFileString(filename: string, s: string): void {
+function writeFileString(filename: string, s: string) {
   const enc = new TextEncoder();
   const data = enc.encode(s);
   Deno.writeFileSync(filename, data, { mode: 0o666 });
@@ -127,7 +127,7 @@ function writeFileString(filename: string, s: string): void {
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  function renameSyncErrorsUnix(): void {
+  function renameSyncErrorsUnix() {
     const testDir = Deno.makeTempDirSync();
     const oldfile = testDir + "/oldfile";
     const olddir = testDir + "/olddir";
@@ -141,21 +141,21 @@ unitTest(
     writeFileString(file, "world");
 
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(oldfile, emptydir);
       },
       Error,
       "Is a directory",
     );
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, fulldir);
       },
       Error,
       "Directory not empty",
     );
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, file);
       },
       Error,
@@ -170,21 +170,21 @@ unitTest(
     Deno.symlinkSync(testDir + "/nonexistent", danglingLink);
 
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, fileLink);
       },
       Error,
       "Not a directory",
     );
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, dirLink);
       },
       Error,
       "Not a directory",
     );
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, danglingLink);
       },
       Error,
@@ -202,7 +202,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os !== "windows", perms: { read: true, write: true } },
-  function renameSyncErrorsWin(): void {
+  function renameSyncErrorsWin() {
     const testDir = Deno.makeTempDirSync();
     const oldfile = testDir + "/oldfile";
     const olddir = testDir + "/olddir";
@@ -216,21 +216,21 @@ unitTest(
     writeFileString(file, "world");
 
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(oldfile, emptydir);
       },
       Deno.errors.PermissionDenied,
       "Access is denied",
     );
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, fulldir);
       },
       Deno.errors.PermissionDenied,
       "Access is denied",
     );
     assertThrows(
-      (): void => {
+      () => {
         Deno.renameSync(olddir, emptydir);
       },
       Deno.errors.PermissionDenied,
diff --git a/cli/tests/unit/request_test.ts b/cli/tests/unit/request_test.ts
index dca9e4a73..8f31d7d5d 100644
--- a/cli/tests/unit/request_test.ts
+++ b/cli/tests/unit/request_test.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertEquals, assertStringIncludes, unitTest } from "./test_util.ts";
 
-unitTest(async function fromInit(): Promise<void> {
+unitTest(async function fromInit() {
   const req = new Request("http://foo/", {
     body: "ahoyhoy",
     method: "POST",
@@ -15,7 +15,7 @@ unitTest(async function fromInit(): Promise<void> {
   assertEquals(req.headers.get("test-header"), "value");
 });
 
-unitTest(function requestNonString(): void {
+unitTest(function requestNonString() {
   const nonString = {
     toString() {
       return "http://foo/";
@@ -26,18 +26,18 @@ unitTest(function requestNonString(): void {
   assertEquals(new Request(nonString).url, "http://foo/");
 });
 
-unitTest(function methodNonString(): void {
+unitTest(function methodNonString() {
   assertEquals(new Request("http://foo/", { method: undefined }).method, "GET");
 });
 
-unitTest(function requestRelativeUrl(): void {
+unitTest(function requestRelativeUrl() {
   assertEquals(
     new Request("relative-url").url,
     "http://js-unit-tests/foo/relative-url",
   );
 });
 
-unitTest(async function cloneRequestBodyStream(): Promise<void> {
+unitTest(async function cloneRequestBodyStream() {
   // hack to get a stream
   const stream =
     new Request("http://foo/", { body: "a test body", method: "POST" }).body;
@@ -54,7 +54,7 @@ unitTest(async function cloneRequestBodyStream(): Promise<void> {
   assertEquals(b1, b2);
 });
 
-unitTest(function customInspectFunction(): void {
+unitTest(function customInspectFunction() {
   const request = new Request("https://example.com");
   assertEquals(
     Deno.inspect(request),
diff --git a/cli/tests/unit/resources_test.ts b/cli/tests/unit/resources_test.ts
index 96fd4ff2c..ea183a068 100644
--- a/cli/tests/unit/resources_test.ts
+++ b/cli/tests/unit/resources_test.ts
@@ -1,13 +1,13 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, assertEquals, assertThrows, unitTest } from "./test_util.ts";
 
-unitTest(function resourcesCloseBadArgs(): void {
+unitTest(function resourcesCloseBadArgs() {
   assertThrows(() => {
     Deno.close((null as unknown) as number);
   }, TypeError);
 });
 
-unitTest(function resourcesStdio(): void {
+unitTest(function resourcesStdio() {
   const res = Deno.resources();
 
   assertEquals(res[0], "stdin");
@@ -15,9 +15,7 @@ unitTest(function resourcesStdio(): void {
   assertEquals(res[2], "stderr");
 });
 
-unitTest({ perms: { net: true } }, async function resourcesNet(): Promise<
-  void
-> {
+unitTest({ perms: { net: true } }, async function resourcesNet() {
   const listener = Deno.listen({ port: 4501 });
   const dialerConn = await Deno.connect({ port: 4501 });
   const listenerConn = await listener.accept();
@@ -37,9 +35,7 @@ unitTest({ perms: { net: true } }, async function resourcesNet(): Promise<
   listener.close();
 });
 
-unitTest({ perms: { read: true } }, async function resourcesFile(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function resourcesFile() {
   const resourcesBefore = Deno.resources();
   const f = await Deno.open("cli/tests/hello.txt");
   const resourcesAfter = Deno.resources();
diff --git a/cli/tests/unit/response_test.ts b/cli/tests/unit/response_test.ts
index c1ef80fb6..3f6197e1f 100644
--- a/cli/tests/unit/response_test.ts
+++ b/cli/tests/unit/response_test.ts
@@ -56,7 +56,7 @@ unitTest(async function responseFormData() {
   assertEquals([...formData], [...input]);
 });
 
-unitTest(function customInspectFunction(): void {
+unitTest(function customInspectFunction() {
   const response = new Response();
   assertEquals(
     Deno.inspect(response),
diff --git a/cli/tests/unit/signal_test.ts b/cli/tests/unit/signal_test.ts
index 340ec43eb..d0cd40950 100644
--- a/cli/tests/unit/signal_test.ts
+++ b/cli/tests/unit/signal_test.ts
@@ -10,7 +10,7 @@ import {
 
 unitTest(
   { ignore: Deno.build.os !== "windows" },
-  function signalsNotImplemented(): void {
+  function signalsNotImplemented() {
     assertThrows(
       () => {
         Deno.signal(1);
@@ -100,7 +100,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { run: true, net: true } },
-  async function signalStreamTest(): Promise<void> {
+  async function signalStreamTest() {
     const resolvable = deferred();
     // This prevents the program from exiting.
     const t = setInterval(() => {}, 1000);
@@ -132,7 +132,7 @@ unitTest(
 // This tests that pending op_signal_poll doesn't block the runtime from exiting the process.
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { run: true, read: true } },
-  async function signalStreamExitTest(): Promise<void> {
+  async function signalStreamExitTest() {
     const p = Deno.run({
       cmd: [
         Deno.execPath(),
@@ -149,7 +149,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { run: true } },
-  async function signalPromiseTest(): Promise<void> {
+  async function signalPromiseTest() {
     const resolvable = deferred();
     // This prevents the program from exiting.
     const t = setInterval(() => {}, 1000);
@@ -170,7 +170,7 @@ unitTest(
 // https://github.com/denoland/deno/issues/9806
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { run: true } },
-  async function signalPromiseTest2(): Promise<void> {
+  async function signalPromiseTest2() {
     const resolvable = deferred();
     // This prevents the program from exiting.
     const t = setInterval(() => {}, 1000);
@@ -198,7 +198,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { run: true } },
-  function signalShorthandsTest(): void {
+  function signalShorthandsTest() {
     let s: Deno.SignalStream;
     s = Deno.signals.alarm(); // for SIGALRM
     assert(s instanceof Deno.SignalStream);
diff --git a/cli/tests/unit/stat_test.ts b/cli/tests/unit/stat_test.ts
index d75eb22eb..4b663e5b9 100644
--- a/cli/tests/unit/stat_test.ts
+++ b/cli/tests/unit/stat_test.ts
@@ -8,7 +8,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest({ perms: { read: true } }, function fstatSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function fstatSyncSuccess() {
   const file = Deno.openSync("README.md");
   const fileInfo = Deno.fstatSync(file.rid);
   assert(fileInfo.isFile);
@@ -23,9 +23,7 @@ unitTest({ perms: { read: true } }, function fstatSyncSuccess(): void {
   Deno.close(file.rid);
 });
 
-unitTest({ perms: { read: true } }, async function fstatSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function fstatSuccess() {
   const file = await Deno.open("README.md");
   const fileInfo = await Deno.fstat(file.rid);
   assert(fileInfo.isFile);
@@ -42,7 +40,7 @@ unitTest({ perms: { read: true } }, async function fstatSuccess(): Promise<
 
 unitTest(
   { perms: { read: true, write: true } },
-  function statSyncSuccess(): void {
+  function statSyncSuccess() {
     const packageInfo = Deno.statSync("README.md");
     assert(packageInfo.isFile);
     assert(!packageInfo.isSymlink);
@@ -103,19 +101,19 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: false } }, function statSyncPerm(): void {
+unitTest({ perms: { read: false } }, function statSyncPerm() {
   assertThrows(() => {
     Deno.statSync("README.md");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function statSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function statSyncNotFound() {
   assertThrows(() => {
     Deno.statSync("bad_file_name");
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { read: true } }, function lstatSyncSuccess(): void {
+unitTest({ perms: { read: true } }, function lstatSyncSuccess() {
   const packageInfo = Deno.lstatSync("README.md");
   assert(packageInfo.isFile);
   assert(!packageInfo.isSymlink);
@@ -143,13 +141,13 @@ unitTest({ perms: { read: true } }, function lstatSyncSuccess(): void {
   assert(!coreInfoByUrl.isSymlink);
 });
 
-unitTest({ perms: { read: false } }, function lstatSyncPerm(): void {
+unitTest({ perms: { read: false } }, function lstatSyncPerm() {
   assertThrows(() => {
     Deno.lstatSync("README.md");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, function lstatSyncNotFound(): void {
+unitTest({ perms: { read: true } }, function lstatSyncNotFound() {
   assertThrows(() => {
     Deno.lstatSync("bad_file_name");
   }, Deno.errors.NotFound);
@@ -157,7 +155,7 @@ unitTest({ perms: { read: true } }, function lstatSyncNotFound(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function statSuccess(): Promise<void> {
+  async function statSuccess() {
     const packageInfo = await Deno.stat("README.md");
     assert(packageInfo.isFile);
     assert(!packageInfo.isSymlink);
@@ -221,25 +219,21 @@ unitTest(
   },
 );
 
-unitTest({ perms: { read: false } }, async function statPerm(): Promise<void> {
+unitTest({ perms: { read: false } }, async function statPerm() {
   await assertThrowsAsync(async () => {
     await Deno.stat("README.md");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, async function statNotFound(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function statNotFound() {
   await assertThrowsAsync(
-    async (): Promise<void> => {
+    async () => {
       await Deno.stat("bad_file_name"), Deno.errors.NotFound;
     },
   );
 });
 
-unitTest({ perms: { read: true } }, async function lstatSuccess(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function lstatSuccess() {
   const packageInfo = await Deno.lstat("README.md");
   assert(packageInfo.isFile);
   assert(!packageInfo.isSymlink);
@@ -267,15 +261,13 @@ unitTest({ perms: { read: true } }, async function lstatSuccess(): Promise<
   assert(!coreInfoByUrl.isSymlink);
 });
 
-unitTest({ perms: { read: false } }, async function lstatPerm(): Promise<void> {
+unitTest({ perms: { read: false } }, async function lstatPerm() {
   await assertThrowsAsync(async () => {
     await Deno.lstat("README.md");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { read: true } }, async function lstatNotFound(): Promise<
-  void
-> {
+unitTest({ perms: { read: true } }, async function lstatNotFound() {
   await assertThrowsAsync(async () => {
     await Deno.lstat("bad_file_name");
   }, Deno.errors.NotFound);
@@ -283,7 +275,7 @@ unitTest({ perms: { read: true } }, async function lstatNotFound(): Promise<
 
 unitTest(
   { ignore: Deno.build.os !== "windows", perms: { read: true, write: true } },
-  function statNoUnixFields(): void {
+  function statNoUnixFields() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -304,7 +296,7 @@ unitTest(
 
 unitTest(
   { ignore: Deno.build.os === "windows", perms: { read: true, write: true } },
-  function statUnixFields(): void {
+  function statUnixFields() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
diff --git a/cli/tests/unit/symlink_test.ts b/cli/tests/unit/symlink_test.ts
index eef993d17..b9fcd9e7a 100644
--- a/cli/tests/unit/symlink_test.ts
+++ b/cli/tests/unit/symlink_test.ts
@@ -8,7 +8,7 @@ import {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function symlinkSyncSuccess(): void {
+  function symlinkSyncSuccess() {
     const testDir = Deno.makeTempDirSync();
     const oldname = testDir + "/oldname";
     const newname = testDir + "/newname";
@@ -23,7 +23,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function symlinkSyncURL(): void {
+  function symlinkSyncURL() {
     const testDir = Deno.makeTempDirSync();
     const oldname = testDir + "/oldname";
     const newname = testDir + "/newname";
@@ -39,7 +39,7 @@ unitTest(
   },
 );
 
-unitTest(function symlinkSyncPerm(): void {
+unitTest(function symlinkSyncPerm() {
   assertThrows(() => {
     Deno.symlinkSync("oldbaddir", "newbaddir");
   }, Deno.errors.PermissionDenied);
@@ -47,7 +47,7 @@ unitTest(function symlinkSyncPerm(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function symlinkSuccess(): Promise<void> {
+  async function symlinkSuccess() {
     const testDir = Deno.makeTempDirSync();
     const oldname = testDir + "/oldname";
     const newname = testDir + "/newname";
@@ -62,7 +62,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function symlinkURL(): Promise<void> {
+  async function symlinkURL() {
     const testDir = Deno.makeTempDirSync();
     const oldname = testDir + "/oldname";
     const newname = testDir + "/newname";
diff --git a/cli/tests/unit/sync_test.ts b/cli/tests/unit/sync_test.ts
index 98b2f4bd9..c359513eb 100644
--- a/cli/tests/unit/sync_test.ts
+++ b/cli/tests/unit/sync_test.ts
@@ -3,7 +3,7 @@ import { assertEquals, unitTest } from "./test_util.ts";
 
 unitTest(
   { perms: { read: true, write: true } },
-  function fdatasyncSyncSuccess(): void {
+  function fdatasyncSyncSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_fdatasyncSync.txt";
     const file = Deno.openSync(filename, {
       read: true,
@@ -21,7 +21,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function fdatasyncSuccess(): Promise<void> {
+  async function fdatasyncSuccess() {
     const filename = (await Deno.makeTempDir()) + "/test_fdatasync.txt";
     const file = await Deno.open(filename, {
       read: true,
@@ -39,7 +39,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function fsyncSyncSuccess(): void {
+  function fsyncSyncSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_fsyncSync.txt";
     const file = Deno.openSync(filename, {
       read: true,
@@ -57,7 +57,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function fsyncSuccess(): Promise<void> {
+  async function fsyncSuccess() {
     const filename = (await Deno.makeTempDir()) + "/test_fsync.txt";
     const file = await Deno.open(filename, {
       read: true,
diff --git a/cli/tests/unit/testing_test.ts b/cli/tests/unit/testing_test.ts
index 4789dbfa7..89b3cc31f 100644
--- a/cli/tests/unit/testing_test.ts
+++ b/cli/tests/unit/testing_test.ts
@@ -1,12 +1,12 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assertThrows, unitTest } from "./test_util.ts";
 
-unitTest(function testFnOverloading(): void {
+unitTest(function testFnOverloading() {
   // just verifying that you can use this test definition syntax
-  Deno.test("test fn overloading", (): void => {});
+  Deno.test("test fn overloading", () => {});
 });
 
-unitTest(function nameOfTestCaseCantBeEmpty(): void {
+unitTest(function nameOfTestCaseCantBeEmpty() {
   assertThrows(
     () => {
       Deno.test("", () => {});
diff --git a/cli/tests/unit/text_encoding_test.ts b/cli/tests/unit/text_encoding_test.ts
index 42c221cb2..a65a4176b 100644
--- a/cli/tests/unit/text_encoding_test.ts
+++ b/cli/tests/unit/text_encoding_test.ts
@@ -1,19 +1,19 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, assertEquals, assertThrows, unitTest } from "./test_util.ts";
 
-unitTest(function btoaSuccess(): void {
+unitTest(function btoaSuccess() {
   const text = "hello world";
   const encoded = btoa(text);
   assertEquals(encoded, "aGVsbG8gd29ybGQ=");
 });
 
-unitTest(function atobSuccess(): void {
+unitTest(function atobSuccess() {
   const encoded = "aGVsbG8gd29ybGQ=";
   const decoded = atob(encoded);
   assertEquals(decoded, "hello world");
 });
 
-unitTest(function atobWithAsciiWhitespace(): void {
+unitTest(function atobWithAsciiWhitespace() {
   const encodedList = [
     " aGVsbG8gd29ybGQ=",
     "  aGVsbG8gd29ybGQ=",
@@ -30,7 +30,7 @@ unitTest(function atobWithAsciiWhitespace(): void {
   }
 });
 
-unitTest(function atobThrows(): void {
+unitTest(function atobThrows() {
   let threw = false;
   try {
     atob("aGVsbG8gd29ybGQ==");
@@ -40,7 +40,7 @@ unitTest(function atobThrows(): void {
   assert(threw);
 });
 
-unitTest(function atobThrows2(): void {
+unitTest(function atobThrows2() {
   let threw = false;
   try {
     atob("aGVsbG8gd29ybGQ===");
@@ -50,7 +50,7 @@ unitTest(function atobThrows2(): void {
   assert(threw);
 });
 
-unitTest(function atobThrows3(): void {
+unitTest(function atobThrows3() {
   let threw = false;
   try {
     atob("foobar!!");
@@ -65,14 +65,14 @@ unitTest(function atobThrows3(): void {
   assert(threw);
 });
 
-unitTest(function btoaFailed(): void {
+unitTest(function btoaFailed() {
   const text = "你好";
   assertThrows(() => {
     btoa(text);
   }, DOMException);
 });
 
-unitTest(function textDecoder2(): void {
+unitTest(function textDecoder2() {
   // deno-fmt-ignore
   const fixture = new Uint8Array([
     0xf0, 0x9d, 0x93, 0xbd,
@@ -86,13 +86,13 @@ unitTest(function textDecoder2(): void {
 
 // ignoreBOM is tested through WPT
 
-unitTest(function textDecoderASCII(): void {
+unitTest(function textDecoderASCII() {
   const fixture = new Uint8Array([0x89, 0x95, 0x9f, 0xbf]);
   const decoder = new TextDecoder("ascii");
   assertEquals(decoder.decode(fixture), "‰•Ÿ¿");
 });
 
-unitTest(function textDecoderErrorEncoding(): void {
+unitTest(function textDecoderErrorEncoding() {
   let didThrow = false;
   try {
     new TextDecoder("Foo");
@@ -103,7 +103,7 @@ unitTest(function textDecoderErrorEncoding(): void {
   assert(didThrow);
 });
 
-unitTest(function textEncoder(): void {
+unitTest(function textEncoder() {
   const fixture = "𝓽𝓮𝔁𝓽";
   const encoder = new TextEncoder();
   // deno-fmt-ignore
@@ -115,7 +115,7 @@ unitTest(function textEncoder(): void {
   ]);
 });
 
-unitTest(function textEncodeInto(): void {
+unitTest(function textEncodeInto() {
   const fixture = "text";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(5);
@@ -128,7 +128,7 @@ unitTest(function textEncodeInto(): void {
   ]);
 });
 
-unitTest(function textEncodeInto2(): void {
+unitTest(function textEncodeInto2() {
   const fixture = "𝓽𝓮𝔁𝓽";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(17);
@@ -144,7 +144,7 @@ unitTest(function textEncodeInto2(): void {
   ]);
 });
 
-unitTest(function textEncodeInto3(): void {
+unitTest(function textEncodeInto3() {
   const fixture = "𝓽𝓮𝔁𝓽";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(5);
@@ -157,7 +157,7 @@ unitTest(function textEncodeInto3(): void {
   ]);
 });
 
-unitTest(function loneSurrogateEncodeInto(): void {
+unitTest(function loneSurrogateEncodeInto() {
   const fixture = "lone𝄞\ud888surrogate";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(20);
@@ -174,7 +174,7 @@ unitTest(function loneSurrogateEncodeInto(): void {
   ]);
 });
 
-unitTest(function loneSurrogateEncodeInto2(): void {
+unitTest(function loneSurrogateEncodeInto2() {
   const fixture = "\ud800";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(3);
@@ -187,7 +187,7 @@ unitTest(function loneSurrogateEncodeInto2(): void {
   ]);
 });
 
-unitTest(function loneSurrogateEncodeInto3(): void {
+unitTest(function loneSurrogateEncodeInto3() {
   const fixture = "\udc00";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(3);
@@ -200,7 +200,7 @@ unitTest(function loneSurrogateEncodeInto3(): void {
   ]);
 });
 
-unitTest(function swappedSurrogatePairEncodeInto4(): void {
+unitTest(function swappedSurrogatePairEncodeInto4() {
   const fixture = "\udc00\ud800";
   const encoder = new TextEncoder();
   const bytes = new Uint8Array(8);
@@ -213,7 +213,7 @@ unitTest(function swappedSurrogatePairEncodeInto4(): void {
   ]);
 });
 
-unitTest(function textDecoderSharedUint8Array(): void {
+unitTest(function textDecoderSharedUint8Array() {
   const ab = new SharedArrayBuffer(6);
   const dataView = new DataView(ab);
   const charCodeA = "A".charCodeAt(0);
@@ -226,7 +226,7 @@ unitTest(function textDecoderSharedUint8Array(): void {
   assertEquals(actual, "ABCDEF");
 });
 
-unitTest(function textDecoderSharedInt32Array(): void {
+unitTest(function textDecoderSharedInt32Array() {
   const ab = new SharedArrayBuffer(8);
   const dataView = new DataView(ab);
   const charCodeA = "A".charCodeAt(0);
@@ -239,14 +239,14 @@ unitTest(function textDecoderSharedInt32Array(): void {
   assertEquals(actual, "ABCDEFGH");
 });
 
-unitTest(function toStringShouldBeWebCompatibility(): void {
+unitTest(function toStringShouldBeWebCompatibility() {
   const encoder = new TextEncoder();
   assertEquals(encoder.toString(), "[object TextEncoder]");
 
   const decoder = new TextDecoder();
   assertEquals(decoder.toString(), "[object TextDecoder]");
 });
-unitTest(function textEncoderShouldCoerceToString(): void {
+unitTest(function textEncoderShouldCoerceToString() {
   const encoder = new TextEncoder();
   const fixutreText = "text";
   const fixture = {
diff --git a/cli/tests/unit/timers_test.ts b/cli/tests/unit/timers_test.ts
index cb5f541d7..4eb470ba9 100644
--- a/cli/tests/unit/timers_test.ts
+++ b/cli/tests/unit/timers_test.ts
@@ -9,11 +9,11 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest(async function functionParameterBindingSuccess(): Promise<void> {
+unitTest(async function functionParameterBindingSuccess() {
   const promise = deferred();
   let count = 0;
 
-  const nullProto = (newCount: number): void => {
+  const nullProto = (newCount: number) => {
     count = newCount;
     promise.resolve();
   };
@@ -26,7 +26,7 @@ unitTest(async function functionParameterBindingSuccess(): Promise<void> {
   assertEquals(count, 1);
 });
 
-unitTest(async function stringifyAndEvalNonFunctions(): Promise<void> {
+unitTest(async function stringifyAndEvalNonFunctions() {
   // eval can only access global scope
   const global = globalThis as unknown as {
     globalPromise: ReturnType<typeof deferred>;
@@ -50,10 +50,10 @@ unitTest(async function stringifyAndEvalNonFunctions(): Promise<void> {
   Reflect.deleteProperty(global, "globalCount");
 });
 
-unitTest(async function timeoutSuccess(): Promise<void> {
+unitTest(async function timeoutSuccess() {
   const promise = deferred();
   let count = 0;
-  setTimeout((): void => {
+  setTimeout(() => {
     count++;
     promise.resolve();
   }, 500);
@@ -62,7 +62,7 @@ unitTest(async function timeoutSuccess(): Promise<void> {
   assertEquals(count, 1);
 });
 
-unitTest(async function timeoutEvalNoScopeLeak(): Promise<void> {
+unitTest(async function timeoutEvalNoScopeLeak() {
   // eval can only access global scope
   const global = globalThis as unknown as {
     globalPromise: Deferred<Error>;
@@ -83,11 +83,11 @@ unitTest(async function timeoutEvalNoScopeLeak(): Promise<void> {
   Reflect.deleteProperty(global, "globalPromise");
 });
 
-unitTest(async function timeoutArgs(): Promise<void> {
+unitTest(async function timeoutArgs() {
   const promise = deferred();
   const arg = 1;
   setTimeout(
-    (a, b, c): void => {
+    (a, b, c) => {
       assertEquals(a, arg);
       assertEquals(b, arg.toString());
       assertEquals(c, [arg]);
@@ -101,9 +101,9 @@ unitTest(async function timeoutArgs(): Promise<void> {
   await promise;
 });
 
-unitTest(async function timeoutCancelSuccess(): Promise<void> {
+unitTest(async function timeoutCancelSuccess() {
   let count = 0;
-  const id = setTimeout((): void => {
+  const id = setTimeout(() => {
     count++;
   }, 1);
   // Cancelled, count should not increment
@@ -112,7 +112,7 @@ unitTest(async function timeoutCancelSuccess(): Promise<void> {
   assertEquals(count, 0);
 });
 
-unitTest(async function timeoutCancelMultiple(): Promise<void> {
+unitTest(async function timeoutCancelMultiple() {
   function uncalled(): never {
     throw new Error("This function should not be called.");
   }
@@ -137,11 +137,11 @@ unitTest(async function timeoutCancelMultiple(): Promise<void> {
   await delay(50);
 });
 
-unitTest(async function timeoutCancelInvalidSilentFail(): Promise<void> {
+unitTest(async function timeoutCancelInvalidSilentFail() {
   // Expect no panic
   const promise = deferred();
   let count = 0;
-  const id = setTimeout((): void => {
+  const id = setTimeout(() => {
     count++;
     // Should have no effect
     clearTimeout(id);
@@ -154,10 +154,10 @@ unitTest(async function timeoutCancelInvalidSilentFail(): Promise<void> {
   clearTimeout(2147483647);
 });
 
-unitTest(async function intervalSuccess(): Promise<void> {
+unitTest(async function intervalSuccess() {
   const promise = deferred();
   let count = 0;
-  const id = setInterval((): void => {
+  const id = setInterval(() => {
     count++;
     clearInterval(id);
     promise.resolve();
@@ -172,9 +172,9 @@ unitTest(async function intervalSuccess(): Promise<void> {
   await delay(0);
 });
 
-unitTest(async function intervalCancelSuccess(): Promise<void> {
+unitTest(async function intervalCancelSuccess() {
   let count = 0;
-  const id = setInterval((): void => {
+  const id = setInterval(() => {
     count++;
   }, 1);
   clearInterval(id);
@@ -182,10 +182,10 @@ unitTest(async function intervalCancelSuccess(): Promise<void> {
   assertEquals(count, 0);
 });
 
-unitTest(async function intervalOrdering(): Promise<void> {
+unitTest(async function intervalOrdering() {
   const timers: number[] = [];
   let timeouts = 0;
-  function onTimeout(): void {
+  function onTimeout() {
     ++timeouts;
     for (let i = 1; i < timers.length; i++) {
       clearTimeout(timers[i]);
@@ -198,26 +198,24 @@ unitTest(async function intervalOrdering(): Promise<void> {
   assertEquals(timeouts, 1);
 });
 
-unitTest(function intervalCancelInvalidSilentFail(): void {
+unitTest(function intervalCancelInvalidSilentFail() {
   // Should silently fail (no panic)
   clearInterval(2147483647);
 });
 
-unitTest(async function fireCallbackImmediatelyWhenDelayOverMaxValue(): Promise<
-  void
-> {
+unitTest(async function fireCallbackImmediatelyWhenDelayOverMaxValue() {
   let count = 0;
-  setTimeout((): void => {
+  setTimeout(() => {
     count++;
   }, 2 ** 31);
   await delay(1);
   assertEquals(count, 1);
 });
 
-unitTest(async function timeoutCallbackThis(): Promise<void> {
+unitTest(async function timeoutCallbackThis() {
   const promise = deferred();
   const obj = {
-    foo(): void {
+    foo() {
       assertEquals(this, window);
       promise.resolve();
     },
@@ -226,7 +224,7 @@ unitTest(async function timeoutCallbackThis(): Promise<void> {
   await promise;
 });
 
-unitTest(async function timeoutBindThis(): Promise<void> {
+unitTest(async function timeoutBindThis() {
   const thisCheckPassed = [null, undefined, window, globalThis];
 
   const thisCheckFailed = [
@@ -237,7 +235,7 @@ unitTest(async function timeoutBindThis(): Promise<void> {
     {},
     [],
     "foo",
-    (): void => {},
+    () => {},
     Object.prototype,
   ];
 
@@ -274,7 +272,7 @@ unitTest(async function timeoutBindThis(): Promise<void> {
   }
 });
 
-unitTest(function clearTimeoutShouldConvertToNumber(): void {
+unitTest(function clearTimeoutShouldConvertToNumber() {
   let called = false;
   const obj = {
     valueOf(): number {
@@ -286,10 +284,10 @@ unitTest(function clearTimeoutShouldConvertToNumber(): void {
   assert(called);
 });
 
-unitTest(function setTimeoutShouldThrowWithBigint(): void {
+unitTest(function setTimeoutShouldThrowWithBigint() {
   let hasThrown = 0;
   try {
-    setTimeout((): void => {}, (1n as unknown) as number);
+    setTimeout(() => {}, (1n as unknown) as number);
     hasThrown = 1;
   } catch (err) {
     if (err instanceof TypeError) {
@@ -301,7 +299,7 @@ unitTest(function setTimeoutShouldThrowWithBigint(): void {
   assertEquals(hasThrown, 2);
 });
 
-unitTest(function clearTimeoutShouldThrowWithBigint(): void {
+unitTest(function clearTimeoutShouldThrowWithBigint() {
   let hasThrown = 0;
   try {
     clearTimeout((1n as unknown) as number);
@@ -316,23 +314,23 @@ unitTest(function clearTimeoutShouldThrowWithBigint(): void {
   assertEquals(hasThrown, 2);
 });
 
-unitTest(function testFunctionName(): void {
+unitTest(function testFunctionName() {
   assertEquals(clearTimeout.name, "clearTimeout");
   assertEquals(clearInterval.name, "clearInterval");
 });
 
-unitTest(function testFunctionParamsLength(): void {
+unitTest(function testFunctionParamsLength() {
   assertEquals(setTimeout.length, 1);
   assertEquals(setInterval.length, 1);
   assertEquals(clearTimeout.length, 0);
   assertEquals(clearInterval.length, 0);
 });
 
-unitTest(function clearTimeoutAndClearIntervalNotBeEquals(): void {
+unitTest(function clearTimeoutAndClearIntervalNotBeEquals() {
   assertNotEquals(clearTimeout, clearInterval);
 });
 
-unitTest(async function timerMaxCpuBug(): Promise<void> {
+unitTest(async function timerMaxCpuBug() {
   // There was a bug where clearing a timeout would cause Deno to use 100% CPU.
   clearTimeout(setTimeout(() => {}, 1000));
   // We can check this by counting how many ops have triggered in the interim.
@@ -343,7 +341,7 @@ unitTest(async function timerMaxCpuBug(): Promise<void> {
   assert(opsDispatched_ - opsDispatched < 10);
 });
 
-unitTest(async function timerBasicMicrotaskOrdering(): Promise<void> {
+unitTest(async function timerBasicMicrotaskOrdering() {
   let s = "";
   let count = 0;
   const promise = deferred();
@@ -367,7 +365,7 @@ unitTest(async function timerBasicMicrotaskOrdering(): Promise<void> {
   assertEquals(s, "deno");
 });
 
-unitTest(async function timerNestedMicrotaskOrdering(): Promise<void> {
+unitTest(async function timerNestedMicrotaskOrdering() {
   let s = "";
   const promise = deferred();
   s += "0";
@@ -407,7 +405,7 @@ unitTest(function testQueueMicrotask() {
   assertEquals(typeof queueMicrotask, "function");
 });
 
-unitTest(async function timerIgnoresDateOverride(): Promise<void> {
+unitTest(async function timerIgnoresDateOverride() {
   const OriginalDate = Date;
   const promise = deferred();
   let hasThrown = 0;
@@ -416,7 +414,7 @@ unitTest(async function timerIgnoresDateOverride(): Promise<void> {
       promise.reject("global Date override used over original Date object");
       return 0;
     };
-    const DateOverride = (): void => {
+    const DateOverride = () => {
       overrideCalled();
     };
     globalThis.Date = DateOverride as DateConstructor;
@@ -441,7 +439,7 @@ unitTest(async function timerIgnoresDateOverride(): Promise<void> {
   assertEquals(hasThrown, 1);
 });
 
-unitTest({ perms: { hrtime: true } }, function sleepSync(): void {
+unitTest({ perms: { hrtime: true } }, function sleepSync() {
   const start = performance.now();
   Deno.sleepSync(10);
   const after = performance.now();
@@ -450,7 +448,7 @@ unitTest({ perms: { hrtime: true } }, function sleepSync(): void {
 
 unitTest(
   { perms: { hrtime: true } },
-  async function sleepSyncShorterPromise(): Promise<void> {
+  async function sleepSyncShorterPromise() {
     const perf = performance;
     const short = 5;
     const long = 10;
@@ -469,7 +467,7 @@ unitTest(
 
 unitTest(
   { perms: { hrtime: true } },
-  async function sleepSyncLongerPromise(): Promise<void> {
+  async function sleepSyncLongerPromise() {
     const perf = performance;
     const short = 5;
     const long = 10;
diff --git a/cli/tests/unit/tls_test.ts b/cli/tests/unit/tls_test.ts
index cedcf467d..46a27b7f0 100644
--- a/cli/tests/unit/tls_test.ts
+++ b/cli/tests/unit/tls_test.ts
@@ -16,7 +16,7 @@ import { TextProtoReader } from "../../../test_util/std/textproto/mod.ts";
 const encoder = new TextEncoder();
 const decoder = new TextDecoder();
 
-async function sleep(msec: number): Promise<void> {
+async function sleep(msec: number) {
   await new Promise((res, _rej) => setTimeout(res, msec));
 }
 
@@ -24,7 +24,7 @@ function unreachable(): never {
   throw new Error("Unreachable code reached");
 }
 
-unitTest(async function connectTLSNoPerm(): Promise<void> {
+unitTest(async function connectTLSNoPerm() {
   await assertThrowsAsync(async () => {
     await Deno.connectTls({ hostname: "github.com", port: 443 });
   }, Deno.errors.PermissionDenied);
@@ -32,7 +32,7 @@ unitTest(async function connectTLSNoPerm(): Promise<void> {
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function connectTLSInvalidHost(): Promise<void> {
+  async function connectTLSInvalidHost() {
     const listener = await Deno.listenTls({
       hostname: "localhost",
       port: 3567,
@@ -48,7 +48,7 @@ unitTest(
   },
 );
 
-unitTest(async function connectTLSCertFileNoReadPerm(): Promise<void> {
+unitTest(async function connectTLSCertFileNoReadPerm() {
   await assertThrowsAsync(async () => {
     await Deno.connectTls({
       hostname: "github.com",
@@ -60,7 +60,7 @@ unitTest(async function connectTLSCertFileNoReadPerm(): Promise<void> {
 
 unitTest(
   { perms: { read: true, net: true } },
-  function listenTLSNonExistentCertKeyFiles(): void {
+  function listenTLSNonExistentCertKeyFiles() {
     const options = {
       hostname: "localhost",
       port: 3500,
@@ -84,7 +84,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { net: true } }, function listenTLSNoReadPerm(): void {
+unitTest({ perms: { net: true } }, function listenTLSNoReadPerm() {
   assertThrows(() => {
     Deno.listenTls({
       hostname: "localhost",
@@ -99,7 +99,7 @@ unitTest(
   {
     perms: { read: true, write: true, net: true },
   },
-  function listenTLSEmptyKeyFile(): void {
+  function listenTLSEmptyKeyFile() {
     const options = {
       hostname: "localhost",
       port: 3500,
@@ -124,7 +124,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true, net: true } },
-  function listenTLSEmptyCertFile(): void {
+  function listenTLSEmptyCertFile() {
     const options = {
       hostname: "localhost",
       port: 3500,
@@ -149,7 +149,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function dialAndListenTLS(): Promise<void> {
+  async function dialAndListenTLS() {
     const resolvable = deferred();
     const hostname = "localhost";
     const port = 3500;
@@ -166,7 +166,7 @@ unitTest(
     );
 
     listener.accept().then(
-      async (conn): Promise<void> => {
+      async (conn) => {
         assert(conn.remoteAddr != null);
         assert(conn.localAddr != null);
         await conn.write(response);
@@ -242,7 +242,7 @@ async function sendThenCloseWriteThenReceive(
   conn: Deno.Conn,
   chunkCount: number,
   chunkSize: number,
-): Promise<void> {
+) {
   const byteCount = chunkCount * chunkSize;
   const buf = new Uint8Array(chunkSize); // Note: buf is size of _chunk_.
   let n: number;
@@ -274,7 +274,7 @@ async function receiveThenSend(
   conn: Deno.Conn,
   chunkCount: number,
   chunkSize: number,
-): Promise<void> {
+) {
   const byteCount = chunkCount * chunkSize;
   const buf = new Uint8Array(byteCount); // Note: buf size equals `byteCount`.
   let n: number;
@@ -301,7 +301,7 @@ async function receiveThenSend(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsServerStreamHalfCloseSendOneByte(): Promise<void> {
+  async function tlsServerStreamHalfCloseSendOneByte() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(serverConn, 1, 1),
@@ -312,7 +312,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientStreamHalfCloseSendOneByte(): Promise<void> {
+  async function tlsClientStreamHalfCloseSendOneByte() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(clientConn, 1, 1),
@@ -323,7 +323,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsServerStreamHalfCloseSendOneChunk(): Promise<void> {
+  async function tlsServerStreamHalfCloseSendOneChunk() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(serverConn, 1, 1 << 20 /* 1 MB */),
@@ -334,7 +334,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientStreamHalfCloseSendOneChunk(): Promise<void> {
+  async function tlsClientStreamHalfCloseSendOneChunk() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(clientConn, 1, 1 << 20 /* 1 MB */),
@@ -345,7 +345,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsServerStreamHalfCloseSendManyBytes(): Promise<void> {
+  async function tlsServerStreamHalfCloseSendManyBytes() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(serverConn, 100, 1),
@@ -356,7 +356,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientStreamHalfCloseSendManyBytes(): Promise<void> {
+  async function tlsClientStreamHalfCloseSendManyBytes() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(clientConn, 100, 1),
@@ -367,7 +367,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsServerStreamHalfCloseSendManyChunks(): Promise<void> {
+  async function tlsServerStreamHalfCloseSendManyChunks() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(serverConn, 100, 1 << 16 /* 64 kB */),
@@ -378,7 +378,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientStreamHalfCloseSendManyChunks(): Promise<void> {
+  async function tlsClientStreamHalfCloseSendManyChunks() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendThenCloseWriteThenReceive(clientConn, 100, 1 << 16 /* 64 kB */),
@@ -387,7 +387,7 @@ unitTest(
   },
 );
 
-async function sendAlotReceiveNothing(conn: Deno.Conn): Promise<void> {
+async function sendAlotReceiveNothing(conn: Deno.Conn) {
   // Start receive op.
   const readBuf = new Uint8Array(1024);
   const readPromise = conn.read(readBuf);
@@ -410,7 +410,7 @@ async function sendAlotReceiveNothing(conn: Deno.Conn): Promise<void> {
   );
 }
 
-async function receiveAlotSendNothing(conn: Deno.Conn): Promise<void> {
+async function receiveAlotSendNothing(conn: Deno.Conn) {
   const readBuf = new Uint8Array(1024);
   let n: number | null;
 
@@ -428,7 +428,7 @@ async function receiveAlotSendNothing(conn: Deno.Conn): Promise<void> {
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsServerStreamCancelRead(): Promise<void> {
+  async function tlsServerStreamCancelRead() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendAlotReceiveNothing(serverConn),
@@ -439,7 +439,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientStreamCancelRead(): Promise<void> {
+  async function tlsClientStreamCancelRead() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendAlotReceiveNothing(clientConn),
@@ -448,7 +448,7 @@ unitTest(
   },
 );
 
-async function sendReceiveEmptyBuf(conn: Deno.Conn): Promise<void> {
+async function sendReceiveEmptyBuf(conn: Deno.Conn) {
   const byteBuf = new Uint8Array([1]);
   const emptyBuf = new Uint8Array(0);
   let n: number | null;
@@ -485,7 +485,7 @@ async function sendReceiveEmptyBuf(conn: Deno.Conn): Promise<void> {
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsStreamSendReceiveEmptyBuf(): Promise<void> {
+  async function tlsStreamSendReceiveEmptyBuf() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       sendReceiveEmptyBuf(serverConn),
@@ -494,12 +494,12 @@ unitTest(
   },
 );
 
-function immediateClose(conn: Deno.Conn): Promise<void> {
+function immediateClose(conn: Deno.Conn) {
   conn.close();
   return Promise.resolve();
 }
 
-async function closeWriteAndClose(conn: Deno.Conn): Promise<void> {
+async function closeWriteAndClose(conn: Deno.Conn) {
   await conn.closeWrite();
 
   if (await conn.read(new Uint8Array(1)) !== null) {
@@ -511,7 +511,7 @@ async function closeWriteAndClose(conn: Deno.Conn): Promise<void> {
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsServerStreamImmediateClose(): Promise<void> {
+  async function tlsServerStreamImmediateClose() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       immediateClose(serverConn),
@@ -522,7 +522,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientStreamImmediateClose(): Promise<void> {
+  async function tlsClientStreamImmediateClose() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       closeWriteAndClose(serverConn),
@@ -533,7 +533,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function tlsClientAndServerStreamImmediateClose(): Promise<void> {
+  async function tlsClientAndServerStreamImmediateClose() {
     const [serverConn, clientConn] = await tlsPair();
     await Promise.all([
       immediateClose(serverConn),
@@ -547,7 +547,7 @@ async function tlsWithTcpFailureTestImpl(
   cipherByteCount: number,
   failureMode: "corruption" | "shutdown",
   reverse: boolean,
-): Promise<void> {
+) {
   const tlsPort = getPort();
   const tlsListener = Deno.listenTls({
     hostname: "localhost",
@@ -723,7 +723,7 @@ async function tlsWithTcpFailureTestImpl(
     conn: Deno.Conn,
     byte: number,
     count: number,
-  ): Promise<void> {
+  ) {
     let buf = new Uint8Array(1 << 12 /* 4 kB */);
     buf.fill(byte);
 
@@ -739,7 +739,7 @@ async function tlsWithTcpFailureTestImpl(
     conn: Deno.Conn,
     byte: number,
     count: number,
-  ): Promise<void> {
+  ) {
     let buf = new Uint8Array(1 << 12 /* 4 kB */);
     while (count > 0) {
       buf = buf.subarray(0, Math.min(buf.length, count));
@@ -761,7 +761,7 @@ async function tlsWithTcpFailureTestImpl(
     sink: Deno.Conn,
     count: number,
     interruptPromise: Deferred<void>,
-  ): Promise<void> {
+  ) {
     let buf = new Uint8Array(1 << 12 /* 4 kB */);
     while (count > 0) {
       buf = buf.subarray(0, Math.min(buf.length, count));
@@ -913,7 +913,7 @@ async function curl(url: string): Promise<string> {
 
 unitTest(
   { perms: { read: true, net: true, run: true } },
-  async function curlFakeHttpsServer(): Promise<void> {
+  async function curlFakeHttpsServer() {
     const port = getPort();
     const listener = createHttpsListener(port);
 
@@ -937,7 +937,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, net: true } },
-  async function startTls(): Promise<void> {
+  async function startTls() {
     const hostname = "smtp.gmail.com";
     const port = 587;
     const encoder = new TextEncoder();
diff --git a/cli/tests/unit/truncate_test.ts b/cli/tests/unit/truncate_test.ts
index 19cb9328a..14309d0c1 100644
--- a/cli/tests/unit/truncate_test.ts
+++ b/cli/tests/unit/truncate_test.ts
@@ -8,7 +8,7 @@ import {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function ftruncateSyncSuccess(): void {
+  function ftruncateSyncSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_ftruncateSync.txt";
     const file = Deno.openSync(filename, {
       create: true,
@@ -30,7 +30,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function ftruncateSuccess(): Promise<void> {
+  async function ftruncateSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_ftruncate.txt";
     const file = await Deno.open(filename, {
       create: true,
@@ -52,7 +52,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function truncateSyncSuccess(): void {
+  function truncateSyncSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_truncateSync.txt";
     Deno.writeFileSync(filename, new Uint8Array(5));
     Deno.truncateSync(filename, 20);
@@ -67,7 +67,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function truncateSuccess(): Promise<void> {
+  async function truncateSuccess() {
     const filename = Deno.makeTempDirSync() + "/test_truncate.txt";
     await Deno.writeFile(filename, new Uint8Array(5));
     await Deno.truncate(filename, 20);
@@ -80,15 +80,13 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: false } }, function truncateSyncPerm(): void {
+unitTest({ perms: { write: false } }, function truncateSyncPerm() {
   assertThrows(() => {
     Deno.truncateSync("/test_truncateSyncPermission.txt");
   }, Deno.errors.PermissionDenied);
 });
 
-unitTest({ perms: { write: false } }, async function truncatePerm(): Promise<
-  void
-> {
+unitTest({ perms: { write: false } }, async function truncatePerm() {
   await assertThrowsAsync(async () => {
     await Deno.truncate("/test_truncatePermission.txt");
   }, Deno.errors.PermissionDenied);
diff --git a/cli/tests/unit/tty_test.ts b/cli/tests/unit/tty_test.ts
index 8f9b95372..a9f1105f6 100644
--- a/cli/tests/unit/tty_test.ts
+++ b/cli/tests/unit/tty_test.ts
@@ -3,7 +3,7 @@ import { assert, assertThrows, unitTest } from "./test_util.ts";
 
 // Note tests for Deno.setRaw is in integration tests.
 
-unitTest({ perms: { read: true } }, function consoleSizeFile(): void {
+unitTest({ perms: { read: true } }, function consoleSizeFile() {
   const file = Deno.openSync("cli/tests/hello.txt");
   assertThrows(() => {
     Deno.consoleSize(file.rid);
@@ -11,21 +11,21 @@ unitTest({ perms: { read: true } }, function consoleSizeFile(): void {
   file.close();
 });
 
-unitTest(function consoleSizeError(): void {
+unitTest(function consoleSizeError() {
   assertThrows(() => {
     // Absurdly large rid.
     Deno.consoleSize(0x7fffffff);
   }, Deno.errors.BadResource);
 });
 
-unitTest({ perms: { read: true } }, function isatty(): void {
+unitTest({ perms: { read: true } }, function isatty() {
   // CI not under TTY, so cannot test stdin/stdout/stderr.
   const f = Deno.openSync("cli/tests/hello.txt");
   assert(!Deno.isatty(f.rid));
   f.close();
 });
 
-unitTest(function isattyError(): void {
+unitTest(function isattyError() {
   let caught = false;
   try {
     // Absurdly large rid.
diff --git a/cli/tests/unit/umask_test.ts b/cli/tests/unit/umask_test.ts
index aa10b15eb..579208ee0 100644
--- a/cli/tests/unit/umask_test.ts
+++ b/cli/tests/unit/umask_test.ts
@@ -5,7 +5,7 @@ unitTest(
   {
     ignore: Deno.build.os === "windows",
   },
-  function umaskSuccess(): void {
+  function umaskSuccess() {
     const prevMask = Deno.umask(0o020);
     const newMask = Deno.umask(prevMask);
     const finalMask = Deno.umask();
diff --git a/cli/tests/unit/url_search_params_test.ts b/cli/tests/unit/url_search_params_test.ts
index c4df86a7f..0d6e1f236 100644
--- a/cli/tests/unit/url_search_params_test.ts
+++ b/cli/tests/unit/url_search_params_test.ts
@@ -1,13 +1,13 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 import { assert, assertEquals, unitTest } from "./test_util.ts";
 
-unitTest(function urlSearchParamsWithMultipleSpaces(): void {
+unitTest(function urlSearchParamsWithMultipleSpaces() {
   const init = { str: "this string has spaces in it" };
   const searchParams = new URLSearchParams(init).toString();
   assertEquals(searchParams, "str=this+string+has+spaces+in+it");
 });
 
-unitTest(function urlSearchParamsWithExclamation(): void {
+unitTest(function urlSearchParamsWithExclamation() {
   const init = [
     ["str", "hello, world!"],
   ];
@@ -15,7 +15,7 @@ unitTest(function urlSearchParamsWithExclamation(): void {
   assertEquals(searchParams, "str=hello%2C+world%21");
 });
 
-unitTest(function urlSearchParamsWithQuotes(): void {
+unitTest(function urlSearchParamsWithQuotes() {
   const init = [
     ["str", "'hello world'"],
   ];
@@ -23,7 +23,7 @@ unitTest(function urlSearchParamsWithQuotes(): void {
   assertEquals(searchParams, "str=%27hello+world%27");
 });
 
-unitTest(function urlSearchParamsWithBraket(): void {
+unitTest(function urlSearchParamsWithBraket() {
   const init = [
     ["str", "(hello world)"],
   ];
@@ -31,7 +31,7 @@ unitTest(function urlSearchParamsWithBraket(): void {
   assertEquals(searchParams, "str=%28hello+world%29");
 });
 
-unitTest(function urlSearchParamsWithTilde(): void {
+unitTest(function urlSearchParamsWithTilde() {
   const init = [
     ["str", "hello~world"],
   ];
@@ -39,7 +39,7 @@ unitTest(function urlSearchParamsWithTilde(): void {
   assertEquals(searchParams, "str=hello%7Eworld");
 });
 
-unitTest(function urlSearchParamsInitString(): void {
+unitTest(function urlSearchParamsInitString() {
   const init = "c=4&a=2&b=3&%C3%A1=1";
   const searchParams = new URLSearchParams(init);
   assert(
@@ -48,7 +48,7 @@ unitTest(function urlSearchParamsInitString(): void {
   );
 });
 
-unitTest(function urlSearchParamsInitStringWithPlusCharacter(): void {
+unitTest(function urlSearchParamsInitStringWithPlusCharacter() {
   let params = new URLSearchParams("q=a+b");
   assertEquals(params.toString(), "q=a+b");
   assertEquals(params.get("q"), "a b");
@@ -58,7 +58,7 @@ unitTest(function urlSearchParamsInitStringWithPlusCharacter(): void {
   assertEquals(params.get("q"), "a b c");
 });
 
-unitTest(function urlSearchParamsInitStringWithMalformedParams(): void {
+unitTest(function urlSearchParamsInitStringWithMalformedParams() {
   // These test cases are copied from Web Platform Tests
   // https://github.com/web-platform-tests/wpt/blob/54c6d64/url/urlsearchparams-constructor.any.js#L60-L80
   let params = new URLSearchParams("id=0&value=%");
@@ -84,7 +84,7 @@ unitTest(function urlSearchParamsInitStringWithMalformedParams(): void {
   assertEquals(params.get("b"), "%*");
 });
 
-unitTest(function urlSearchParamsInitIterable(): void {
+unitTest(function urlSearchParamsInitIterable() {
   const init = [
     ["a", "54"],
     ["b", "true"],
@@ -93,13 +93,13 @@ unitTest(function urlSearchParamsInitIterable(): void {
   assertEquals(searchParams.toString(), "a=54&b=true");
 });
 
-unitTest(function urlSearchParamsInitRecord(): void {
+unitTest(function urlSearchParamsInitRecord() {
   const init = { a: "54", b: "true" };
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.toString(), "a=54&b=true");
 });
 
-unitTest(function urlSearchParamsInit(): void {
+unitTest(function urlSearchParamsInit() {
   const params1 = new URLSearchParams("a=b");
   assertEquals(params1.toString(), "a=b");
   // deno-lint-ignore no-explicit-any
@@ -107,20 +107,20 @@ unitTest(function urlSearchParamsInit(): void {
   assertEquals(params2.toString(), "a=b");
 });
 
-unitTest(function urlSearchParamsAppendSuccess(): void {
+unitTest(function urlSearchParamsAppendSuccess() {
   const searchParams = new URLSearchParams();
   searchParams.append("a", "true");
   assertEquals(searchParams.toString(), "a=true");
 });
 
-unitTest(function urlSearchParamsDeleteSuccess(): void {
+unitTest(function urlSearchParamsDeleteSuccess() {
   const init = "a=54&b=true";
   const searchParams = new URLSearchParams(init);
   searchParams.delete("b");
   assertEquals(searchParams.toString(), "a=54");
 });
 
-unitTest(function urlSearchParamsGetAllSuccess(): void {
+unitTest(function urlSearchParamsGetAllSuccess() {
   const init = "a=54&b=true&a=true";
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.getAll("a"), ["54", "true"]);
@@ -128,7 +128,7 @@ unitTest(function urlSearchParamsGetAllSuccess(): void {
   assertEquals(searchParams.getAll("c"), []);
 });
 
-unitTest(function urlSearchParamsGetSuccess(): void {
+unitTest(function urlSearchParamsGetSuccess() {
   const init = "a=54&b=true&a=true";
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.get("a"), "54");
@@ -136,7 +136,7 @@ unitTest(function urlSearchParamsGetSuccess(): void {
   assertEquals(searchParams.get("c"), null);
 });
 
-unitTest(function urlSearchParamsHasSuccess(): void {
+unitTest(function urlSearchParamsHasSuccess() {
   const init = "a=54&b=true&a=true";
   const searchParams = new URLSearchParams(init);
   assert(searchParams.has("a"));
@@ -144,35 +144,35 @@ unitTest(function urlSearchParamsHasSuccess(): void {
   assert(!searchParams.has("c"));
 });
 
-unitTest(function urlSearchParamsSetReplaceFirstAndRemoveOthers(): void {
+unitTest(function urlSearchParamsSetReplaceFirstAndRemoveOthers() {
   const init = "a=54&b=true&a=true";
   const searchParams = new URLSearchParams(init);
   searchParams.set("a", "false");
   assertEquals(searchParams.toString(), "a=false&b=true");
 });
 
-unitTest(function urlSearchParamsSetAppendNew(): void {
+unitTest(function urlSearchParamsSetAppendNew() {
   const init = "a=54&b=true&a=true";
   const searchParams = new URLSearchParams(init);
   searchParams.set("c", "foo");
   assertEquals(searchParams.toString(), "a=54&b=true&a=true&c=foo");
 });
 
-unitTest(function urlSearchParamsSortSuccess(): void {
+unitTest(function urlSearchParamsSortSuccess() {
   const init = "c=4&a=2&b=3&a=1";
   const searchParams = new URLSearchParams(init);
   searchParams.sort();
   assertEquals(searchParams.toString(), "a=2&a=1&b=3&c=4");
 });
 
-unitTest(function urlSearchParamsForEachSuccess(): void {
+unitTest(function urlSearchParamsForEachSuccess() {
   const init = [
     ["a", "54"],
     ["b", "true"],
   ];
   const searchParams = new URLSearchParams(init);
   let callNum = 0;
-  searchParams.forEach((value, key, parent): void => {
+  searchParams.forEach((value, key, parent) => {
     assertEquals(searchParams, parent);
     assertEquals(value, init[callNum][1]);
     assertEquals(key, init[callNum][0]);
@@ -181,34 +181,34 @@ unitTest(function urlSearchParamsForEachSuccess(): void {
   assertEquals(callNum, init.length);
 });
 
-unitTest(function urlSearchParamsMissingName(): void {
+unitTest(function urlSearchParamsMissingName() {
   const init = "=4";
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.get(""), "4");
   assertEquals(searchParams.toString(), "=4");
 });
 
-unitTest(function urlSearchParamsMissingValue(): void {
+unitTest(function urlSearchParamsMissingValue() {
   const init = "4=";
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.get("4"), "");
   assertEquals(searchParams.toString(), "4=");
 });
 
-unitTest(function urlSearchParamsMissingEqualSign(): void {
+unitTest(function urlSearchParamsMissingEqualSign() {
   const init = "4";
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.get("4"), "");
   assertEquals(searchParams.toString(), "4=");
 });
 
-unitTest(function urlSearchParamsMissingPair(): void {
+unitTest(function urlSearchParamsMissingPair() {
   const init = "c=4&&a=54&";
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.toString(), "c=4&a=54");
 });
 
-unitTest(function urlSearchParamsForShortEncodedChar(): void {
+unitTest(function urlSearchParamsForShortEncodedChar() {
   const init = { linefeed: "\n", tab: "\t" };
   const searchParams = new URLSearchParams(init);
   assertEquals(searchParams.toString(), "linefeed=%0A&tab=%09");
@@ -216,7 +216,7 @@ unitTest(function urlSearchParamsForShortEncodedChar(): void {
 
 // If pair does not contain exactly two items, then throw a TypeError.
 // ref https://url.spec.whatwg.org/#interface-urlsearchparams
-unitTest(function urlSearchParamsShouldThrowTypeError(): void {
+unitTest(function urlSearchParamsShouldThrowTypeError() {
   let hasThrown = 0;
 
   try {
@@ -246,14 +246,14 @@ unitTest(function urlSearchParamsShouldThrowTypeError(): void {
   assertEquals(hasThrown, 2);
 });
 
-unitTest(function urlSearchParamsAppendArgumentsCheck(): void {
+unitTest(function urlSearchParamsAppendArgumentsCheck() {
   const methodRequireOneParam = ["delete", "getAll", "get", "has", "forEach"];
 
   const methodRequireTwoParams = ["append", "set"];
 
   methodRequireOneParam
     .concat(methodRequireTwoParams)
-    .forEach((method: string): void => {
+    .forEach((method: string) => {
       const searchParams = new URLSearchParams();
       let hasThrown = 0;
       try {
@@ -270,7 +270,7 @@ unitTest(function urlSearchParamsAppendArgumentsCheck(): void {
       assertEquals(hasThrown, 2);
     });
 
-  methodRequireTwoParams.forEach((method: string): void => {
+  methodRequireTwoParams.forEach((method: string) => {
     const searchParams = new URLSearchParams();
     let hasThrown = 0;
     try {
@@ -289,7 +289,7 @@ unitTest(function urlSearchParamsAppendArgumentsCheck(): void {
 });
 
 // ref: https://github.com/web-platform-tests/wpt/blob/master/url/urlsearchparams-delete.any.js
-unitTest(function urlSearchParamsDeletingAppendedMultiple(): void {
+unitTest(function urlSearchParamsDeletingAppendedMultiple() {
   const params = new URLSearchParams();
   params.append("first", (1 as unknown) as string);
   assert(params.has("first"));
@@ -303,7 +303,7 @@ unitTest(function urlSearchParamsDeletingAppendedMultiple(): void {
 });
 
 // ref: https://github.com/web-platform-tests/wpt/blob/master/url/urlsearchparams-constructor.any.js#L176-L182
-unitTest(function urlSearchParamsCustomSymbolIterator(): void {
+unitTest(function urlSearchParamsCustomSymbolIterator() {
   const params = new URLSearchParams();
   params[Symbol.iterator] = function* (): IterableIterator<[string, string]> {
     yield ["a", "b"];
@@ -313,7 +313,7 @@ unitTest(function urlSearchParamsCustomSymbolIterator(): void {
 });
 
 unitTest(
-  function urlSearchParamsCustomSymbolIteratorWithNonStringParams(): void {
+  function urlSearchParamsCustomSymbolIteratorWithNonStringParams() {
     const params = {};
     // deno-lint-ignore no-explicit-any
     (params as any)[Symbol.iterator] = function* (): IterableIterator<
@@ -328,10 +328,10 @@ unitTest(
 
 // If a class extends URLSearchParams, override one method should not change another's behavior.
 unitTest(
-  function urlSearchParamsOverridingAppendNotChangeConstructorAndSet(): void {
+  function urlSearchParamsOverridingAppendNotChangeConstructorAndSet() {
     let overridedAppendCalled = 0;
     class CustomSearchParams extends URLSearchParams {
-      append(name: string, value: string): void {
+      append(name: string, value: string) {
         ++overridedAppendCalled;
         super.append(name, value);
       }
@@ -344,7 +344,7 @@ unitTest(
   },
 );
 
-unitTest(function urlSearchParamsOverridingEntriesNotChangeForEach(): void {
+unitTest(function urlSearchParamsOverridingEntriesNotChangeForEach() {
   class CustomSearchParams extends URLSearchParams {
     *entries(): IterableIterator<[string, string]> {
       yield* [];
diff --git a/cli/tests/unit/url_test.ts b/cli/tests/unit/url_test.ts
index 8d280ccb5..9f32445a9 100644
--- a/cli/tests/unit/url_test.ts
+++ b/cli/tests/unit/url_test.ts
@@ -7,7 +7,7 @@ import {
   unitTest,
 } from "./test_util.ts";
 
-unitTest(function urlParsing(): void {
+unitTest(function urlParsing() {
   const url = new URL(
     "https://foo:bar@baz.qat:8000/qux/quux?foo=bar&baz=12#qat",
   );
@@ -33,7 +33,7 @@ unitTest(function urlParsing(): void {
   );
 });
 
-unitTest(function urlProtocolParsing(): void {
+unitTest(function urlProtocolParsing() {
   assertEquals(new URL("Aa+-.1://foo").protocol, "aa+-.1:");
   assertEquals(new URL("aA+-.1://foo").protocol, "aa+-.1:");
   assertThrows(() => new URL("1://foo"), TypeError, "Invalid URL");
@@ -50,7 +50,7 @@ unitTest(function urlProtocolParsing(): void {
   assertThrows(() => new URL("*://foo"), TypeError, "Invalid URL");
 });
 
-unitTest(function urlAuthenticationParsing(): void {
+unitTest(function urlAuthenticationParsing() {
   const specialUrl = new URL("http://foo:bar@baz");
   assertEquals(specialUrl.username, "foo");
   assertEquals(specialUrl.password, "bar");
@@ -62,7 +62,7 @@ unitTest(function urlAuthenticationParsing(): void {
   assertEquals(nonSpecialUrl.hostname, "baz");
 });
 
-unitTest(function urlHostnameParsing(): void {
+unitTest(function urlHostnameParsing() {
   // IPv6.
   assertEquals(new URL("http://[::1]").hostname, "[::1]");
   assertEquals(new URL("file://[::1]").hostname, "[::1]");
@@ -102,7 +102,7 @@ unitTest(function urlHostnameParsing(): void {
   assertThrows(() => new URL("http://4294967296"), TypeError, "Invalid URL");
 });
 
-unitTest(function urlPortParsing(): void {
+unitTest(function urlPortParsing() {
   const specialUrl = new URL("http://foo:8000");
   assertEquals(specialUrl.hostname, "foo");
   assertEquals(specialUrl.port, "8000");
@@ -112,7 +112,7 @@ unitTest(function urlPortParsing(): void {
   assertEquals(nonSpecialUrl.port, "8000");
 });
 
-unitTest(function urlModifications(): void {
+unitTest(function urlModifications() {
   const url = new URL(
     "https://foo:bar@baz.qat:8000/qux/quux?foo=bar&baz=12#qat",
   );
@@ -167,7 +167,7 @@ unitTest(function urlModifications(): void {
   );
 });
 
-unitTest(function urlModifyHref(): void {
+unitTest(function urlModifyHref() {
   const url = new URL("http://example.com/");
   url.href = "https://foo:bar@example.com:8080/baz/qat#qux";
   assertEquals(url.protocol, "https:");
@@ -179,13 +179,13 @@ unitTest(function urlModifyHref(): void {
   assertEquals(url.hash, "#qux");
 });
 
-unitTest(function urlNormalize(): void {
+unitTest(function urlNormalize() {
   const url = new URL("http://example.com");
   assertEquals(url.pathname, "/");
   assertEquals(url.href, "http://example.com/");
 });
 
-unitTest(function urlModifyPathname(): void {
+unitTest(function urlModifyPathname() {
   const url = new URL("http://foo.bar/baz%qat/qux%quux");
   assertEquals(url.pathname, "/baz%qat/qux%quux");
   // Self-assignment is to invoke the setter.
@@ -201,7 +201,7 @@ unitTest(function urlModifyPathname(): void {
   assertEquals(url.pathname, "/a/b/c");
 });
 
-unitTest(function urlModifyHash(): void {
+unitTest(function urlModifyHash() {
   const url = new URL("http://foo.bar");
   url.hash = "%foo bar/qat%qux#bar";
   assertEquals(url.hash, "#%foo%20bar/qat%qux#bar");
@@ -210,7 +210,7 @@ unitTest(function urlModifyHash(): void {
   assertEquals(url.hash, "#%foo%20bar/qat%qux#bar");
 });
 
-unitTest(function urlSearchParamsReuse(): void {
+unitTest(function urlSearchParamsReuse() {
   const url = new URL(
     "https://foo:bar@baz.qat:8000/qux/quux?foo=bar&baz=12#qat",
   );
@@ -219,7 +219,7 @@ unitTest(function urlSearchParamsReuse(): void {
   assert(sp === url.searchParams, "Search params should be reused.");
 });
 
-unitTest(function urlBackSlashes(): void {
+unitTest(function urlBackSlashes() {
   const url = new URL(
     "https:\\\\foo:bar@baz.qat:8000\\qux\\quux?foo=bar&baz=12#qat",
   );
@@ -229,7 +229,7 @@ unitTest(function urlBackSlashes(): void {
   );
 });
 
-unitTest(function urlProtocolSlashes(): void {
+unitTest(function urlProtocolSlashes() {
   assertEquals(new URL("http:foo").href, "http://foo/");
   assertEquals(new URL("http://foo").href, "http://foo/");
   assertEquals(new URL("file:foo").href, "file:///foo");
@@ -238,7 +238,7 @@ unitTest(function urlProtocolSlashes(): void {
   assertEquals(new URL("abcd://foo").href, "abcd://foo");
 });
 
-unitTest(function urlRequireHost(): void {
+unitTest(function urlRequireHost() {
   assertEquals(new URL("file:///").href, "file:///");
   assertThrows(() => new URL("ftp:///"), TypeError, "Invalid URL");
   assertThrows(() => new URL("http:///"), TypeError, "Invalid URL");
@@ -320,7 +320,7 @@ unitTest(function urlEncoding() {
   );
 });
 
-unitTest(function urlBase(): void {
+unitTest(function urlBase() {
   assertEquals(new URL("d", new URL("http://foo/a?b#c")).href, "http://foo/d");
 
   assertEquals(new URL("", "http://foo/a/b?c#d").href, "http://foo/a/b?c");
@@ -377,7 +377,7 @@ unitTest(function urlSameProtocolBase() {
   assertEquals(new URL("abcd:b", "abcd://foo/a").href, "abcd:b");
 });
 
-unitTest(function deletingAllParamsRemovesQuestionMarkFromURL(): void {
+unitTest(function deletingAllParamsRemovesQuestionMarkFromURL() {
   const url = new URL("http://example.com/?param1&param2");
   url.searchParams.delete("param1");
   url.searchParams.delete("param2");
@@ -385,7 +385,7 @@ unitTest(function deletingAllParamsRemovesQuestionMarkFromURL(): void {
   assertEquals(url.search, "");
 });
 
-unitTest(function removingNonExistentParamRemovesQuestionMarkFromURL(): void {
+unitTest(function removingNonExistentParamRemovesQuestionMarkFromURL() {
   const url = new URL("http://example.com/?");
   assertEquals(url.href, "http://example.com/?");
   url.searchParams.delete("param1");
@@ -393,7 +393,7 @@ unitTest(function removingNonExistentParamRemovesQuestionMarkFromURL(): void {
   assertEquals(url.search, "");
 });
 
-unitTest(function sortingNonExistentParamRemovesQuestionMarkFromURL(): void {
+unitTest(function sortingNonExistentParamRemovesQuestionMarkFromURL() {
   const url = new URL("http://example.com/?");
   assertEquals(url.href, "http://example.com/?");
   url.searchParams.sort();
@@ -401,7 +401,7 @@ unitTest(function sortingNonExistentParamRemovesQuestionMarkFromURL(): void {
   assertEquals(url.search, "");
 });
 
-unitTest(function customInspectFunction(): void {
+unitTest(function customInspectFunction() {
   const url = new URL("http://example.com/?");
   assertEquals(
     Deno.inspect(url),
@@ -428,7 +428,7 @@ unitTest(function protocolNotHttpOrFile() {
   assertEquals(url.origin, "null");
 });
 
-unitTest(function throwForInvalidPortConstructor(): void {
+unitTest(function throwForInvalidPortConstructor() {
   const urls = [
     // If port is greater than 2^16 − 1, validation error, return failure.
     `https://baz.qat:${2 ** 16}`,
@@ -447,7 +447,7 @@ unitTest(function throwForInvalidPortConstructor(): void {
   new URL("https://baz.qat:0");
 });
 
-unitTest(function doNotOverridePortIfInvalid(): void {
+unitTest(function doNotOverridePortIfInvalid() {
   const initialPort = "3000";
   const url = new URL(`https://deno.land:${initialPort}`);
   // If port is greater than 2^16 − 1, validation error, return failure.
@@ -455,7 +455,7 @@ unitTest(function doNotOverridePortIfInvalid(): void {
   assertEquals(url.port, initialPort);
 });
 
-unitTest(function emptyPortForSchemeDefaultPort(): void {
+unitTest(function emptyPortForSchemeDefaultPort() {
   const nonDefaultPort = "3500";
 
   const url = new URL("ftp://baz.qat:21");
diff --git a/cli/tests/unit/utime_test.ts b/cli/tests/unit/utime_test.ts
index 32b631406..f5647d220 100644
--- a/cli/tests/unit/utime_test.ts
+++ b/cli/tests/unit/utime_test.ts
@@ -9,7 +9,7 @@ import {
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function futimeSyncSuccess(): Promise<void> {
+  async function futimeSyncSuccess() {
     const testDir = await Deno.makeTempDir();
     const filename = testDir + "/file.txt";
     const file = await Deno.open(filename, {
@@ -31,7 +31,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function futimeSyncSuccess(): void {
+  function futimeSyncSuccess() {
     const testDir = Deno.makeTempDirSync();
     const filename = testDir + "/file.txt";
     const file = Deno.openSync(filename, {
@@ -53,7 +53,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function utimeSyncFileSuccess(): void {
+  function utimeSyncFileSuccess() {
     const testDir = Deno.makeTempDirSync();
     const filename = testDir + "/file.txt";
     Deno.writeFileSync(filename, new TextEncoder().encode("hello"), {
@@ -72,7 +72,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function utimeSyncUrlSuccess(): void {
+  function utimeSyncUrlSuccess() {
     const testDir = Deno.makeTempDirSync();
     const filename = testDir + "/file.txt";
     Deno.writeFileSync(filename, new TextEncoder().encode("hello"), {
@@ -91,7 +91,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function utimeSyncDirectorySuccess(): void {
+  function utimeSyncDirectorySuccess() {
     const testDir = Deno.makeTempDirSync();
 
     const atime = 1000;
@@ -106,7 +106,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function utimeSyncDateSuccess(): void {
+  function utimeSyncDateSuccess() {
     const testDir = Deno.makeTempDirSync();
 
     const atime = new Date(1000_000);
@@ -139,7 +139,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function utimeSyncLargeNumberSuccess(): void {
+  function utimeSyncLargeNumberSuccess() {
     const testDir = Deno.makeTempDirSync();
 
     // There are Rust side caps (might be fs relate),
@@ -156,7 +156,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function utimeSyncNotFound(): void {
+  function utimeSyncNotFound() {
     const atime = 1000;
     const mtime = 50000;
 
@@ -168,7 +168,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: false } },
-  function utimeSyncPerm(): void {
+  function utimeSyncPerm() {
     const atime = 1000;
     const mtime = 50000;
 
@@ -180,7 +180,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function utimeFileSuccess(): Promise<void> {
+  async function utimeFileSuccess() {
     const testDir = Deno.makeTempDirSync();
     const filename = testDir + "/file.txt";
     Deno.writeFileSync(filename, new TextEncoder().encode("hello"), {
@@ -199,7 +199,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function utimeUrlSuccess(): Promise<void> {
+  async function utimeUrlSuccess() {
     const testDir = Deno.makeTempDirSync();
     const filename = testDir + "/file.txt";
     Deno.writeFileSync(filename, new TextEncoder().encode("hello"), {
@@ -218,7 +218,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function utimeDirectorySuccess(): Promise<void> {
+  async function utimeDirectorySuccess() {
     const testDir = Deno.makeTempDirSync();
 
     const atime = 1000;
@@ -233,7 +233,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function utimeDateSuccess(): Promise<void> {
+  async function utimeDateSuccess() {
     const testDir = Deno.makeTempDirSync();
 
     const atime = new Date(100_000);
@@ -248,7 +248,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function utimeFileDateSuccess(): Promise<void> {
+  async function utimeFileDateSuccess() {
     const testDir = Deno.makeTempDirSync();
     const filename = testDir + "/file.txt";
     Deno.writeFileSync(filename, new TextEncoder().encode("hello"), {
@@ -267,7 +267,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function utimeNotFound(): Promise<void> {
+  async function utimeNotFound() {
     const atime = 1000;
     const mtime = 50000;
 
@@ -279,7 +279,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: false } },
-  async function utimeSyncPerm(): Promise<void> {
+  async function utimeSyncPerm() {
     const atime = 1000;
     const mtime = 50000;
 
diff --git a/cli/tests/unit/version_test.ts b/cli/tests/unit/version_test.ts
index d3a5270c9..e6e95ff07 100644
--- a/cli/tests/unit/version_test.ts
+++ b/cli/tests/unit/version_test.ts
@@ -1,6 +1,6 @@
 import { assert, unitTest } from "./test_util.ts";
 
-unitTest(function version(): void {
+unitTest(function version() {
   const pattern = /^\d+\.\d+\.\d+/;
   assert(pattern.test(Deno.version.deno));
   assert(pattern.test(Deno.version.v8));
diff --git a/cli/tests/unit/wasm_test.ts b/cli/tests/unit/wasm_test.ts
index 27391cbf2..66fcacade 100644
--- a/cli/tests/unit/wasm_test.ts
+++ b/cli/tests/unit/wasm_test.ts
@@ -22,7 +22,7 @@ const simpleWasm = new Uint8Array([
   0x00, 0x20, 0x01, 0x6a, 0x0b
 ]);
 
-unitTest(async function wasmInstantiateWorksWithBuffer(): Promise<void> {
+unitTest(async function wasmInstantiateWorksWithBuffer() {
   const { module, instance } = await WebAssembly.instantiate(simpleWasm);
   assertEquals(WebAssembly.Module.exports(module), [{
     name: "add",
@@ -38,7 +38,7 @@ unitTest(async function wasmInstantiateWorksWithBuffer(): Promise<void> {
 // don't set the WASM streaming callback, is to take a byte source. Here we
 // check that our implementation of the callback disallows it.
 unitTest(
-  async function wasmInstantiateStreamingFailsWithBuffer(): Promise<void> {
+  async function wasmInstantiateStreamingFailsWithBuffer() {
     await assertThrowsAsync(async () => {
       await WebAssembly.instantiateStreaming(
         // Bypassing the type system
@@ -48,7 +48,7 @@ unitTest(
   },
 );
 
-unitTest(async function wasmInstantiateStreaming(): Promise<void> {
+unitTest(async function wasmInstantiateStreaming() {
   let isomorphic = "";
   for (const byte of simpleWasm) {
     isomorphic += String.fromCharCode(byte);
@@ -70,7 +70,7 @@ unitTest(async function wasmInstantiateStreaming(): Promise<void> {
 
 unitTest(
   { perms: { net: true } },
-  async function wasmStreamingNonTrivial(): Promise<void> {
+  async function wasmStreamingNonTrivial() {
     // deno-dom's WASM file is a real-world non-trivial case that gave us
     // trouble when implementing this.
     await WebAssembly.instantiateStreaming(fetch(
diff --git a/cli/tests/unit/write_file_test.ts b/cli/tests/unit/write_file_test.ts
index e63183c4c..4c4cecf43 100644
--- a/cli/tests/unit/write_file_test.ts
+++ b/cli/tests/unit/write_file_test.ts
@@ -8,7 +8,7 @@ import {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeFileSyncSuccess(): void {
+  function writeFileSyncSuccess() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -22,7 +22,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeFileSyncUrl(): void {
+  function writeFileSyncUrl() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = Deno.makeTempDirSync();
@@ -39,7 +39,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: true } }, function writeFileSyncFail(): void {
+unitTest({ perms: { write: true } }, function writeFileSyncFail() {
   const enc = new TextEncoder();
   const data = enc.encode("Hello");
   const filename = "/baddir/test.txt";
@@ -49,7 +49,7 @@ unitTest({ perms: { write: true } }, function writeFileSyncFail(): void {
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { write: false } }, function writeFileSyncPerm(): void {
+unitTest({ perms: { write: false } }, function writeFileSyncPerm() {
   const enc = new TextEncoder();
   const data = enc.encode("Hello");
   const filename = "/baddir/test.txt";
@@ -61,7 +61,7 @@ unitTest({ perms: { write: false } }, function writeFileSyncPerm(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeFileSyncUpdateMode(): void {
+  function writeFileSyncUpdateMode() {
     if (Deno.build.os !== "windows") {
       const enc = new TextEncoder();
       const data = enc.encode("Hello");
@@ -76,7 +76,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeFileSyncCreate(): void {
+  function writeFileSyncCreate() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -97,7 +97,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeFileSyncAppend(): void {
+  function writeFileSyncAppend() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -122,7 +122,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeFileSuccess(): Promise<void> {
+  async function writeFileSuccess() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -136,7 +136,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeFileUrl(): Promise<void> {
+  async function writeFileUrl() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const tempDir = await Deno.makeTempDir();
@@ -155,7 +155,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeFileNotFound(): Promise<void> {
+  async function writeFileNotFound() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = "/baddir/test.txt";
@@ -168,7 +168,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: false } },
-  async function writeFilePerm(): Promise<void> {
+  async function writeFilePerm() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = "/baddir/test.txt";
@@ -181,7 +181,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeFileUpdateMode(): Promise<void> {
+  async function writeFileUpdateMode() {
     if (Deno.build.os !== "windows") {
       const enc = new TextEncoder();
       const data = enc.encode("Hello");
@@ -196,7 +196,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeFileCreate(): Promise<void> {
+  async function writeFileCreate() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -217,7 +217,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeFileAppend(): Promise<void> {
+  async function writeFileAppend() {
     const enc = new TextEncoder();
     const data = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test.txt";
diff --git a/cli/tests/unit/write_text_file_test.ts b/cli/tests/unit/write_text_file_test.ts
index f41f8f663..2d14dc712 100644
--- a/cli/tests/unit/write_text_file_test.ts
+++ b/cli/tests/unit/write_text_file_test.ts
@@ -8,7 +8,7 @@ import {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeTextFileSyncSuccess(): void {
+  function writeTextFileSyncSuccess() {
     const filename = Deno.makeTempDirSync() + "/test.txt";
     Deno.writeTextFileSync(filename, "Hello");
     const dataRead = Deno.readTextFileSync(filename);
@@ -18,7 +18,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeTextFileSyncByUrl(): void {
+  function writeTextFileSyncByUrl() {
     const tempDir = Deno.makeTempDirSync();
     const fileUrl = new URL(
       `file://${Deno.build.os === "windows" ? "/" : ""}${tempDir}/test.txt`,
@@ -31,7 +31,7 @@ unitTest(
   },
 );
 
-unitTest({ perms: { write: true } }, function writeTextFileSyncFail(): void {
+unitTest({ perms: { write: true } }, function writeTextFileSyncFail() {
   const filename = "/baddir/test.txt";
   // The following should fail because /baddir doesn't exist (hopefully).
   assertThrows(() => {
@@ -39,7 +39,7 @@ unitTest({ perms: { write: true } }, function writeTextFileSyncFail(): void {
   }, Deno.errors.NotFound);
 });
 
-unitTest({ perms: { write: false } }, function writeTextFileSyncPerm(): void {
+unitTest({ perms: { write: false } }, function writeTextFileSyncPerm() {
   const filename = "/baddir/test.txt";
   // The following should fail due to no write permission
   assertThrows(() => {
@@ -49,7 +49,7 @@ unitTest({ perms: { write: false } }, function writeTextFileSyncPerm(): void {
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeTextFileSyncUpdateMode(): void {
+  function writeTextFileSyncUpdateMode() {
     if (Deno.build.os !== "windows") {
       const data = "Hello";
       const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -63,7 +63,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeTextFileSyncCreate(): void {
+  function writeTextFileSyncCreate() {
     const data = "Hello";
     const filename = Deno.makeTempDirSync() + "/test.txt";
     let caughtError = false;
@@ -85,7 +85,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  function writeTextFileSyncAppend(): void {
+  function writeTextFileSyncAppend() {
     const data = "Hello";
     const filename = Deno.makeTempDirSync() + "/test.txt";
     Deno.writeTextFileSync(filename, data);
@@ -102,7 +102,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeTextFileSuccess(): Promise<void> {
+  async function writeTextFileSuccess() {
     const filename = Deno.makeTempDirSync() + "/test.txt";
     await Deno.writeTextFile(filename, "Hello");
     const dataRead = Deno.readTextFileSync(filename);
@@ -112,7 +112,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeTextFileByUrl(): Promise<void> {
+  async function writeTextFileByUrl() {
     const tempDir = Deno.makeTempDirSync();
     const fileUrl = new URL(
       `file://${Deno.build.os === "windows" ? "/" : ""}${tempDir}/test.txt`,
@@ -127,7 +127,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeTextFileNotFound(): Promise<void> {
+  async function writeTextFileNotFound() {
     const filename = "/baddir/test.txt";
     // The following should fail because /baddir doesn't exist (hopefully).
     await assertThrowsAsync(async () => {
@@ -138,7 +138,7 @@ unitTest(
 
 unitTest(
   { perms: { write: false } },
-  async function writeTextFilePerm(): Promise<void> {
+  async function writeTextFilePerm() {
     const filename = "/baddir/test.txt";
     // The following should fail due to no write permission
     await assertThrowsAsync(async () => {
@@ -149,7 +149,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeTextFileUpdateMode(): Promise<void> {
+  async function writeTextFileUpdateMode() {
     if (Deno.build.os !== "windows") {
       const data = "Hello";
       const filename = Deno.makeTempDirSync() + "/test.txt";
@@ -163,7 +163,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeTextFileCreate(): Promise<void> {
+  async function writeTextFileCreate() {
     const data = "Hello";
     const filename = Deno.makeTempDirSync() + "/test.txt";
     let caughtError = false;
@@ -185,7 +185,7 @@ unitTest(
 
 unitTest(
   { perms: { read: true, write: true } },
-  async function writeTextFileAppend(): Promise<void> {
+  async function writeTextFileAppend() {
     const data = "Hello";
     const filename = Deno.makeTempDirSync() + "/test.txt";
     await Deno.writeTextFile(filename, data);
diff --git a/cli/tests/websocket_test.ts b/cli/tests/websocket_test.ts
index 8a7fc812c..7d62679fe 100644
--- a/cli/tests/websocket_test.ts
+++ b/cli/tests/websocket_test.ts
@@ -24,28 +24,28 @@ Deno.test("invalid server", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:2121");
   let err = false;
-  ws.onerror = (): void => {
+  ws.onerror = () => {
     err = true;
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     if (err) {
       promise.resolve();
     } else {
       fail();
     }
   };
-  ws.onopen = (): void => fail();
+  ws.onopen = () => fail();
   await promise;
 });
 
 Deno.test("connect & close", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => {
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -56,26 +56,26 @@ Deno.test("connect & abort", async () => {
   const ws = new WebSocket("ws://localhost:4242");
   ws.close();
   let err = false;
-  ws.onerror = (): void => {
+  ws.onerror = () => {
     err = true;
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     if (err) {
       promise.resolve();
     } else {
       fail();
     }
   };
-  ws.onopen = (): void => fail();
+  ws.onopen = () => fail();
   await promise;
 });
 
 Deno.test("connect & close custom valid code", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.close(1000);
-  ws.onclose = (): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.close(1000);
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -84,12 +84,12 @@ Deno.test("connect & close custom valid code", async () => {
 Deno.test("connect & close custom invalid code", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => {
     assertThrows(() => ws.close(1001));
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -98,9 +98,9 @@ Deno.test("connect & close custom invalid code", async () => {
 Deno.test("connect & close custom valid reason", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.close(1000, "foo");
-  ws.onclose = (): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.close(1000, "foo");
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -109,12 +109,12 @@ Deno.test("connect & close custom valid reason", async () => {
 Deno.test("connect & close custom invalid reason", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => {
     assertThrows(() => ws.close(1000, "".padEnd(124, "o")));
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -123,13 +123,13 @@ Deno.test("connect & close custom invalid reason", async () => {
 Deno.test("echo string", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send("foo");
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send("foo");
+  ws.onmessage = (e) => {
     assertEquals(e.data, "foo");
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -139,14 +139,14 @@ Deno.test("echo string tls", async () => {
   const promise1 = deferred();
   const promise2 = deferred();
   const ws = new WebSocket("wss://localhost:4243");
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send("foo");
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send("foo");
+  ws.onmessage = (e) => {
     assertEquals(e.data, "foo");
     ws.close();
     promise1.resolve();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise2.resolve();
   };
   await promise1;
@@ -157,7 +157,7 @@ Deno.test("websocket error", async () => {
   const promise1 = deferred();
   const ws = new WebSocket("wss://localhost:4242");
   ws.onopen = () => fail();
-  ws.onerror = (err): void => {
+  ws.onerror = (err) => {
     assert(err instanceof ErrorEvent);
 
     // Error message got changed because we don't use warp in test_util
@@ -171,9 +171,9 @@ Deno.test("echo blob with binaryType blob", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
   const blob = new Blob(["foo"]);
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send(blob);
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send(blob);
+  ws.onmessage = (e) => {
     e.data.text().then((actual: string) => {
       blob.text().then((expected) => {
         assertEquals(actual, expected);
@@ -181,7 +181,7 @@ Deno.test("echo blob with binaryType blob", async () => {
     });
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -192,15 +192,15 @@ Deno.test("echo blob with binaryType arraybuffer", async () => {
   const ws = new WebSocket("ws://localhost:4242");
   ws.binaryType = "arraybuffer";
   const blob = new Blob(["foo"]);
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send(blob);
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send(blob);
+  ws.onmessage = (e) => {
     blob.arrayBuffer().then((expected) => {
       assertEquals(e.data, expected);
     });
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -210,15 +210,15 @@ Deno.test("echo uint8array with binaryType blob", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
   const uint = new Uint8Array([102, 111, 111]);
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send(uint);
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send(uint);
+  ws.onmessage = (e) => {
     e.data.arrayBuffer().then((actual: ArrayBuffer) => {
       assertEquals(actual, uint.buffer);
     });
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -229,13 +229,13 @@ Deno.test("echo uint8array with binaryType arraybuffer", async () => {
   const ws = new WebSocket("ws://localhost:4242");
   ws.binaryType = "arraybuffer";
   const uint = new Uint8Array([102, 111, 111]);
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send(uint);
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send(uint);
+  ws.onmessage = (e) => {
     assertEquals(e.data, uint.buffer);
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -245,15 +245,15 @@ Deno.test("echo arraybuffer with binaryType blob", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
   const buffer = new ArrayBuffer(3);
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send(buffer);
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send(buffer);
+  ws.onmessage = (e) => {
     e.data.arrayBuffer().then((actual: ArrayBuffer) => {
       assertEquals(actual, buffer);
     });
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -264,13 +264,13 @@ Deno.test("echo arraybuffer with binaryType arraybuffer", async () => {
   const ws = new WebSocket("ws://localhost:4242");
   ws.binaryType = "arraybuffer";
   const buffer = new ArrayBuffer(3);
-  ws.onerror = (): void => fail();
-  ws.onopen = (): void => ws.send(buffer);
-  ws.onmessage = (e): void => {
+  ws.onerror = () => fail();
+  ws.onopen = () => ws.send(buffer);
+  ws.onmessage = (e) => {
     assertEquals(e.data, buffer);
     ws.close();
   };
-  ws.onclose = (): void => {
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -280,7 +280,7 @@ Deno.test("Event Handlers order", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4242");
   const arr: number[] = [];
-  ws.onerror = (): void => fail();
+  ws.onerror = () => fail();
   ws.addEventListener("message", () => arr.push(1));
   ws.onmessage = () => fail();
   ws.addEventListener("message", () => {
@@ -289,8 +289,8 @@ Deno.test("Event Handlers order", async () => {
     assertEquals(arr, [1, 2, 3]);
   });
   ws.onmessage = () => arr.push(2);
-  ws.onopen = (): void => ws.send("Echo");
-  ws.onclose = (): void => {
+  ws.onopen = () => ws.send("Echo");
+  ws.onclose = () => {
     promise.resolve();
   };
   await promise;
@@ -299,8 +299,8 @@ Deno.test("Event Handlers order", async () => {
 Deno.test("Close without frame", async () => {
   const promise = deferred();
   const ws = new WebSocket("ws://localhost:4244");
-  ws.onerror = (): void => fail();
-  ws.onclose = (e): void => {
+  ws.onerror = () => fail();
+  ws.onclose = (e) => {
     assertEquals(e.code, 1005);
     promise.resolve();
   };
diff --git a/cli/tests/workers/bench_large_message.ts b/cli/tests/workers/bench_large_message.ts
index 7f6cb26ce..a89ea9a78 100644
--- a/cli/tests/workers/bench_large_message.ts
+++ b/cli/tests/workers/bench_large_message.ts
@@ -7,7 +7,7 @@ function oneWorker(i: number) {
       new URL("worker_large_message.js", import.meta.url).href,
       { type: "module" },
     );
-    worker.onmessage = (_e): void => {
+    worker.onmessage = (_e) => {
       if (countDown > 0) {
         countDown--;
         return;
diff --git a/cli/tests/workers/bench_round_robin.ts b/cli/tests/workers/bench_round_robin.ts
index 7974760af..a39f7ec6f 100644
--- a/cli/tests/workers/bench_round_robin.ts
+++ b/cli/tests/workers/bench_round_robin.ts
@@ -10,7 +10,7 @@ import { Deferred, deferred } from "../../../test_util/std/async/deferred.ts";
 function handleAsyncMsgFromWorker(
   promiseTable: Map<number, Deferred<string>>,
   msg: { cmdId: number; data: string },
-): void {
+) {
   const promise = promiseTable.get(msg.cmdId);
   if (promise === null) {
     throw new Error(`Failed to find promise: cmdId: ${msg.cmdId}, msg: ${msg}`);
@@ -18,7 +18,7 @@ function handleAsyncMsgFromWorker(
   promise?.resolve(data);
 }
 
-async function main(): Promise<void> {
+async function main() {
   const workers: Array<[Map<number, Deferred<string>>, Worker]> = [];
   for (let i = 1; i <= workerCount; ++i) {
     const worker = new Worker(
@@ -26,7 +26,7 @@ async function main(): Promise<void> {
       { type: "module" },
     );
     const promise = deferred();
-    worker.onmessage = (e): void => {
+    worker.onmessage = (e) => {
       if (e.data.cmdId === 0) promise.resolve();
     };
     worker.postMessage({ cmdId: 0, action: 2 });
@@ -35,7 +35,7 @@ async function main(): Promise<void> {
   }
   // assign callback function
   for (const [promiseTable, worker] of workers) {
-    worker.onmessage = (e): void => {
+    worker.onmessage = (e) => {
       handleAsyncMsgFromWorker(promiseTable, e.data);
     };
   }
@@ -53,7 +53,7 @@ async function main(): Promise<void> {
   }
   for (const [, worker] of workers) {
     const promise = deferred();
-    worker.onmessage = (e): void => {
+    worker.onmessage = (e) => {
       if (e.data.cmdId === 3) promise.resolve();
     };
     worker.postMessage({ action: 3 });
diff --git a/cli/tests/workers/bench_startup.ts b/cli/tests/workers/bench_startup.ts
index 5fbf23b45..bcf21ef44 100644
--- a/cli/tests/workers/bench_startup.ts
+++ b/cli/tests/workers/bench_startup.ts
@@ -1,15 +1,15 @@
 // Benchmark measures time it takes to start and stop a number of workers.
 const workerCount = 50;
 
-async function bench(): Promise<void> {
+async function bench() {
   const workers: Worker[] = [];
   for (let i = 1; i <= workerCount; ++i) {
     const worker = new Worker(
       new URL("bench_worker.ts", import.meta.url).href,
       { type: "module" },
     );
-    const promise = new Promise<void>((resolve): void => {
-      worker.onmessage = (e): void => {
+    const promise = new Promise<void>((resolve) => {
+      worker.onmessage = (e) => {
         if (e.data.cmdId === 0) resolve();
       };
     });
@@ -19,8 +19,8 @@ async function bench(): Promise<void> {
   }
   console.log("Done creating workers closing workers!");
   for (const worker of workers) {
-    const promise = new Promise<void>((resolve): void => {
-      worker.onmessage = (e): void => {
+    const promise = new Promise<void>((resolve) => {
+      worker.onmessage = (e) => {
         if (e.data.cmdId === 3) resolve();
       };
     });
diff --git a/cli/tests/workers/bench_worker.ts b/cli/tests/workers/bench_worker.ts
index 7e85eed03..1edd2750f 100644
--- a/cli/tests/workers/bench_worker.ts
+++ b/cli/tests/workers/bench_worker.ts
@@ -1,4 +1,4 @@
-onmessage = function (e): void {
+onmessage = function (e) {
   const { cmdId, action, data } = e.data;
   switch (action) {
     case 0: // Static response
diff --git a/cli/tests/workers/deno_worker.ts b/cli/tests/workers/deno_worker.ts
index 6a57c47f0..2a29c8c4d 100644
--- a/cli/tests/workers/deno_worker.ts
+++ b/cli/tests/workers/deno_worker.ts
@@ -1,4 +1,4 @@
-onmessage = function (e): void {
+onmessage = function (e) {
   if (typeof self.Deno === "undefined") {
     throw new Error("Deno namespace not available in worker");
   }
diff --git a/cli/tests/workers/test.ts b/cli/tests/workers/test.ts
index d62b644a4..44cbca0fe 100644
--- a/cli/tests/workers/test.ts
+++ b/cli/tests/workers/test.ts
@@ -12,7 +12,7 @@ import { fromFileUrl } from "../../../test_util/std/path/mod.ts";
 
 Deno.test({
   name: "worker terminate",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
 
     const jsWorker = new Worker(
@@ -24,17 +24,17 @@ Deno.test({
       { type: "module", name: "tsWorker" },
     );
 
-    tsWorker.onmessage = (e): void => {
+    tsWorker.onmessage = (e) => {
       assertEquals(e.data, "Hello World");
       promise.resolve();
     };
 
-    jsWorker.onmessage = (e): void => {
+    jsWorker.onmessage = (e) => {
       assertEquals(e.data, "Hello World");
       tsWorker.postMessage("Hello World");
     };
 
-    jsWorker.onerror = (e: Event): void => {
+    jsWorker.onerror = (e: Event) => {
       e.preventDefault();
       jsWorker.postMessage("Hello World");
     };
@@ -55,7 +55,7 @@ Deno.test({
       { type: "module", name: "tsWorker" },
     );
 
-    tsWorker.onmessage = (e): void => {
+    tsWorker.onmessage = (e) => {
       assertEquals(e.data, "Hello World");
       promise.resolve();
     };
@@ -69,7 +69,7 @@ Deno.test({
 
 Deno.test({
   name: "worker nested",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
 
     const nestedWorker = new Worker(
@@ -77,7 +77,7 @@ Deno.test({
       { type: "module", name: "nested" },
     );
 
-    nestedWorker.onmessage = (e): void => {
+    nestedWorker.onmessage = (e) => {
       assert(e.data.type !== "error");
       promise.resolve();
     };
@@ -90,7 +90,7 @@ Deno.test({
 
 Deno.test({
   name: "worker throws when executing",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const throwingWorker = new Worker(
       new URL("throwing_worker.js", import.meta.url).href,
@@ -98,7 +98,7 @@ Deno.test({
     );
 
     // deno-lint-ignore no-explicit-any
-    throwingWorker.onerror = (e: any): void => {
+    throwingWorker.onerror = (e: any) => {
       e.preventDefault();
       assert(/Uncaught Error: Thrown error/.test(e.message));
       promise.resolve();
@@ -111,14 +111,14 @@ Deno.test({
 
 Deno.test({
   name: "worker globals",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const workerOptions: WorkerOptions = { type: "module" };
     const w = new Worker(
       new URL("worker_globals.ts", import.meta.url).href,
       workerOptions,
     );
-    w.onmessage = (e): void => {
+    w.onmessage = (e) => {
       assertEquals(e.data, "true, true, true, true");
       promise.resolve();
     };
@@ -130,7 +130,7 @@ Deno.test({
 
 Deno.test({
   name: "worker fetch API",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
 
     const fetchingWorker = new Worker(
@@ -139,13 +139,13 @@ Deno.test({
     );
 
     // deno-lint-ignore no-explicit-any
-    fetchingWorker.onerror = (e: any): void => {
+    fetchingWorker.onerror = (e: any) => {
       e.preventDefault();
       promise.reject(e.message);
     };
 
     // Defer promise.resolve() to allow worker to shut down
-    fetchingWorker.onmessage = (e): void => {
+    fetchingWorker.onmessage = (e) => {
       assert(e.data === "Done!");
       promise.resolve();
     };
@@ -157,7 +157,7 @@ Deno.test({
 
 Deno.test({
   name: "worker terminate busy loop",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
 
     const busyWorker = new Worker(
@@ -167,11 +167,11 @@ Deno.test({
 
     let testResult = 0;
 
-    busyWorker.onmessage = (e): void => {
+    busyWorker.onmessage = (e) => {
       testResult = e.data;
       if (testResult >= 10000) {
         busyWorker.terminate();
-        busyWorker.onmessage = (_e): void => {
+        busyWorker.onmessage = (_e) => {
           throw new Error("unreachable");
         };
         setTimeout(() => {
@@ -188,7 +188,7 @@ Deno.test({
 
 Deno.test({
   name: "worker race condition",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     // See issue for details
     // https://github.com/denoland/deno/issues/4080
     const promise = deferred();
@@ -198,7 +198,7 @@ Deno.test({
       { type: "module" },
     );
 
-    racyWorker.onmessage = (_e): void => {
+    racyWorker.onmessage = (_e) => {
       setTimeout(() => {
         promise.resolve();
       }, 100);
@@ -211,7 +211,7 @@ Deno.test({
 
 Deno.test({
   name: "worker is event listener",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     let messageHandlersCalled = 0;
     let errorHandlersCalled = 0;
 
@@ -223,7 +223,7 @@ Deno.test({
       { type: "module" },
     );
 
-    worker.onmessage = (_e: Event): void => {
+    worker.onmessage = (_e: Event) => {
       messageHandlersCalled++;
     };
     worker.addEventListener("message", (_e: Event) => {
@@ -234,7 +234,7 @@ Deno.test({
       promise1.resolve();
     });
 
-    worker.onerror = (e): void => {
+    worker.onerror = (e) => {
       errorHandlersCalled++;
       e.preventDefault();
     };
@@ -259,7 +259,7 @@ Deno.test({
 
 Deno.test({
   name: "worker scope is event listener",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise1 = deferred();
 
     const worker = new Worker(
@@ -267,14 +267,14 @@ Deno.test({
       { type: "module" },
     );
 
-    worker.onmessage = (e: MessageEvent): void => {
+    worker.onmessage = (e: MessageEvent) => {
       const { messageHandlersCalled, errorHandlersCalled } = e.data;
       assertEquals(messageHandlersCalled, 4);
       assertEquals(errorHandlersCalled, 4);
       promise1.resolve();
     };
 
-    worker.onerror = (_e): void => {
+    worker.onerror = (_e) => {
       throw new Error("unreachable");
     };
 
@@ -287,7 +287,7 @@ Deno.test({
 
 Deno.test({
   name: "worker with Deno namespace",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const promise2 = deferred();
 
@@ -306,13 +306,13 @@ Deno.test({
       },
     );
 
-    regularWorker.onmessage = (e): void => {
+    regularWorker.onmessage = (e) => {
       assertEquals(e.data, "Hello World");
       regularWorker.terminate();
       promise.resolve();
     };
 
-    denoWorker.onmessage = (e): void => {
+    denoWorker.onmessage = (e) => {
       assertEquals(e.data, "Hello World");
       denoWorker.terminate();
       promise2.resolve();
@@ -327,13 +327,13 @@ Deno.test({
 
 Deno.test({
   name: "worker with crypto in scope",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const w = new Worker(
       new URL("worker_crypto.js", import.meta.url).href,
       { type: "module" },
     );
-    w.onmessage = (e): void => {
+    w.onmessage = (e) => {
       assertEquals(e.data, true);
       promise.resolve();
     };
@@ -345,7 +345,7 @@ Deno.test({
 
 Deno.test({
   name: "Worker event handler order",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const w = new Worker(
       new URL("test_worker.ts", import.meta.url).href,
@@ -353,7 +353,7 @@ Deno.test({
     );
     const arr: number[] = [];
     w.addEventListener("message", () => arr.push(1));
-    w.onmessage = (_e): void => {
+    w.onmessage = (_e) => {
       arr.push(2);
     };
     w.addEventListener("message", () => arr.push(3));
@@ -369,7 +369,7 @@ Deno.test({
 
 Deno.test({
   name: "Worker immediate close",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const w = new Worker(
       new URL("./immediately_close_worker.js", import.meta.url).href,
@@ -385,14 +385,14 @@ Deno.test({
 
 Deno.test({
   name: "Worker post undefined",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const worker = new Worker(
       new URL("./post_undefined.ts", import.meta.url).href,
       { type: "module" },
     );
 
-    const handleWorkerMessage = (e: MessageEvent): void => {
+    const handleWorkerMessage = (e: MessageEvent) => {
       console.log("main <- worker:", e.data);
       worker.terminate();
       promise.resolve();
@@ -650,12 +650,12 @@ Deno.test("Worker with disabled permissions", async function () {
 
 Deno.test({
   name: "worker location",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const workerModuleHref =
       new URL("worker_location.ts", import.meta.url).href;
     const w = new Worker(workerModuleHref, { type: "module" });
-    w.onmessage = (e): void => {
+    w.onmessage = (e) => {
       assertEquals(e.data, `${workerModuleHref}, true`);
       promise.resolve();
     };
@@ -667,14 +667,14 @@ Deno.test({
 
 Deno.test({
   name: "worker with relative specifier",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     assertEquals(location.href, "http://127.0.0.1:4545/cli/tests/");
     const promise = deferred();
     const w = new Worker(
       "./workers/test_worker.ts",
       { type: "module", name: "tsWorker" },
     );
-    w.onmessage = (e): void => {
+    w.onmessage = (e) => {
       assertEquals(e.data, "Hello, world!");
       promise.resolve();
     };
@@ -686,13 +686,13 @@ Deno.test({
 
 Deno.test({
   name: "Worker with top-level-await",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const result = deferred();
     const worker = new Worker(
       new URL("worker_with_top_level_await.ts", import.meta.url).href,
       { type: "module" },
     );
-    worker.onmessage = (e): void => {
+    worker.onmessage = (e) => {
       if (e.data == "ready") {
         worker.postMessage("trigger worker handler");
       } else if (e.data == "triggered worker handler") {
@@ -737,14 +737,14 @@ Deno.test({
 
 Deno.test({
   name: "structured cloning postMessage",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const result = deferred();
     const worker = new Worker(
       new URL("worker_structured_cloning.ts", import.meta.url).href,
       { type: "module" },
     );
 
-    worker.onmessage = (e): void => {
+    worker.onmessage = (e) => {
       // self field should reference itself (circular ref)
       const value = e.data.self.self.self;
 
@@ -772,14 +772,14 @@ Deno.test({
 
 Deno.test({
   name: "worker with relative specifier",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     assertEquals(location.href, "http://127.0.0.1:4545/cli/tests/");
     const promise = deferred();
     const w = new Worker(
       "./workers/test_worker.ts",
       { type: "module", name: "tsWorker" },
     );
-    w.onmessage = (e): void => {
+    w.onmessage = (e) => {
       assertEquals(e.data, "Hello, world!");
       promise.resolve();
     };
@@ -791,7 +791,7 @@ Deno.test({
 
 Deno.test({
   name: "worker SharedArrayBuffer",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const promise = deferred();
     const workerOptions: WorkerOptions = { type: "module" };
     const w = new Worker(
@@ -804,9 +804,9 @@ Deno.test({
     const bytes2 = new Uint8Array(sab2);
     assertEquals(bytes1[0], 0);
     assertEquals(bytes2[0], 0);
-    w.onmessage = (): void => {
+    w.onmessage = () => {
       w.postMessage([sab1, sab2]);
-      w.onmessage = (): void => {
+      w.onmessage = () => {
         assertEquals(bytes1[0], 1);
         assertEquals(bytes2[0], 2);
         promise.resolve();
@@ -819,7 +819,7 @@ Deno.test({
 
 Deno.test({
   name: "Send MessagePorts from / to workers",
-  fn: async function (): Promise<void> {
+  fn: async function () {
     const result = deferred();
     const worker = new Worker(
       new URL("message_port.ts", import.meta.url).href,
diff --git a/cli/tests/workers/test_worker.ts b/cli/tests/workers/test_worker.ts
index ca79dcfe4..996476058 100644
--- a/cli/tests/workers/test_worker.ts
+++ b/cli/tests/workers/test_worker.ts
@@ -2,7 +2,7 @@ if (self.name !== "tsWorker") {
   throw Error(`Invalid worker name: ${self.name}, expected tsWorker`);
 }
 
-onmessage = function (e): void {
+onmessage = function (e) {
   postMessage(e.data);
   close();
 };
diff --git a/cli/tests/workers/worker_globals.ts b/cli/tests/workers/worker_globals.ts
index f26242306..90e369e41 100644
--- a/cli/tests/workers/worker_globals.ts
+++ b/cli/tests/workers/worker_globals.ts
@@ -1,4 +1,4 @@
-onmessage = function (): void {
+onmessage = function () {
   postMessage(
     [
       self instanceof DedicatedWorkerGlobalScope,
diff --git a/cli/tests/workers/worker_location.ts b/cli/tests/workers/worker_location.ts
index 89fa83036..c3c1bb26f 100644
--- a/cli/tests/workers/worker_location.ts
+++ b/cli/tests/workers/worker_location.ts
@@ -1,4 +1,4 @@
-onmessage = function (): void {
+onmessage = function () {
   postMessage(
     `${location.href}, ${location instanceof WorkerLocation}`,
   );
diff --git a/cli/tests/workers/worker_with_top_level_await.ts b/cli/tests/workers/worker_with_top_level_await.ts
index bc77c7932..1d20bb736 100644
--- a/cli/tests/workers/worker_with_top_level_await.ts
+++ b/cli/tests/workers/worker_with_top_level_await.ts
@@ -1,4 +1,4 @@
-function delay(ms: number): Promise<void> {
+function delay(ms: number) {
   return new Promise<void>((resolve) => {
     setTimeout(() => {
       resolve();