Eslint fixes (denoland/deno_std#356)

Make warnings fail
Original: https://github.com/denoland/deno_std/commit/4543b563a9a01c8c168aafcbfd9d4634effba7fc

1 files changed, 2 insertions, 2 deletions

diff --git a/testing/testing_bench.ts b/testing/testing_bench.ts
index 0cc2f233b..9033e3a72 100644
--- a/testing/testing_bench.ts
+++ b/testing/testing_bench.ts
@@ -3,13 +3,13 @@ import { runTests } from "./mod.ts";
 
 import "./asserts_test.ts";
 
-bench(async function testingSerial(b) {
+bench(async function testingSerial(b): Promise<void> {
   b.start();
   await runTests();
   b.stop();
 });
 
-bench(async function testingParallel(b) {
+bench(async function testingParallel(b): Promise<void> {
   b.start();
   await runTests({ parallel: true });
   b.stop();