add assertOps sanitizer in cli/js/ unit tests (#4209)

* add "assertOps" test assertion which makes sure test case
  is not "leaking" ops - ie. after test finishes there are no 
  pending async ops

* apply "assertOps" to all tests in "cli/js/"

* fix numerous tests leaking ops

* document problem with edge case in "clearInterval"
   and "clearTimeout" implementation where they
   may leak async ops

* move "cli/js/worker_test.ts" to "cli/tests/worker_test.ts" and 
  run as integration test; workers leak ops because of missing
  "terminate" implementation

1 files changed, 115 insertions, 0 deletions

diff --git a/cli/tests/workers_test.ts b/cli/tests/workers_test.ts
new file mode 100644
index 000000000..44e7a1776
--- /dev/null
+++ b/cli/tests/workers_test.ts
@@ -0,0 +1,115 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+// Requires to be run with `--allow-net` flag
+
+// FIXME(bartlomieju): this file is an integration test only because
+// workers are leaking ops at the moment - `worker.terminate()` is not
+// yet implemented. Once it gets implemented this file should be
+// again moved to `cli/js/` as an unit test file.
+
+import { assert, assertEquals } from "../../std/testing/asserts.ts";
+
+export interface ResolvableMethods<T> {
+  resolve: (value?: T | PromiseLike<T>) => void;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  reject: (reason?: any) => void;
+}
+
+export type Resolvable<T> = Promise<T> & ResolvableMethods<T>;
+
+export function createResolvable<T>(): Resolvable<T> {
+  let methods: ResolvableMethods<T>;
+  const promise = new Promise<T>((resolve, reject): void => {
+    methods = { resolve, reject };
+  });
+  // TypeScript doesn't know that the Promise callback occurs synchronously
+  // therefore use of not null assertion (`!`)
+  return Object.assign(promise, methods!) as Resolvable<T>;
+}
+
+Deno.test(async function workersBasic(): Promise<void> {
+  const promise = createResolvable();
+  const jsWorker = new Worker("../tests/subdir/test_worker.js", {
+    type: "module",
+    name: "jsWorker"
+  });
+  const tsWorker = new Worker("../tests/subdir/test_worker.ts", {
+    type: "module",
+    name: "tsWorker"
+  });
+
+  tsWorker.onmessage = (e): void => {
+    assertEquals(e.data, "Hello World");
+    promise.resolve();
+  };
+
+  jsWorker.onmessage = (e): void => {
+    assertEquals(e.data, "Hello World");
+    tsWorker.postMessage("Hello World");
+  };
+
+  jsWorker.onerror = (e: Event): void => {
+    e.preventDefault();
+    jsWorker.postMessage("Hello World");
+  };
+
+  jsWorker.postMessage("Hello World");
+  await promise;
+});
+
+Deno.test(async function nestedWorker(): Promise<void> {
+  const promise = createResolvable();
+
+  const nestedWorker = new Worker("../tests/subdir/nested_worker.js", {
+    type: "module",
+    name: "nested"
+  });
+
+  nestedWorker.onmessage = (e): void => {
+    assert(e.data.type !== "error");
+    promise.resolve();
+  };
+
+  nestedWorker.postMessage("Hello World");
+  await promise;
+});
+
+Deno.test(async function workerThrowsWhenExecuting(): Promise<void> {
+  const promise = createResolvable();
+  const throwingWorker = new Worker("../tests/subdir/throwing_worker.js", {
+    type: "module"
+  });
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  throwingWorker.onerror = (e: any): void => {
+    e.preventDefault();
+    assert(/Uncaught Error: Thrown error/.test(e.message));
+    promise.resolve();
+  };
+
+  await promise;
+});
+
+Deno.test(async function workerCanUseFetch(): Promise<void> {
+  const promise = createResolvable();
+
+  const fetchingWorker = new Worker("../tests/subdir/fetching_worker.js", {
+    type: "module"
+  });
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  fetchingWorker.onerror = (e: any): void => {
+    e.preventDefault();
+    promise.reject(e.message);
+  };
+
+  // Defer promise.resolve() to allow worker to shut down
+  fetchingWorker.onmessage = (e): void => {
+    assert(e.data === "Done!");
+    promise.resolve();
+  };
+
+  await promise;
+});
+
+await Deno.runTests();