Add flaky test helper (#620)

packages/miniflare/test/http/fetch.spec.ts

@@ -12,7 +12,7 @@ import {
 	fetch,
 } from "miniflare";
 import { WebSocketServer } from "ws";
-import { useServer } from "../test-shared";
+import { flaky, useServer } from "../test-shared";
 
 const noop = () => {};
 
@@ -109,7 +109,7 @@ test("fetch: includes headers from web socket upgrade response", async (t) => {
 	t.not(res.webSocket, undefined);
 	t.is(res.headers.get("set-cookie"), "key=value");
 });
-test("fetch: dispatches close events on client and server close", async (t) => {
+const fetchDispatchCloseFlakyTest = flaky(async (t) => {
 	let clientCloses = 0;
 	let serverCloses = 0;
 	const clientClosePromise = new DeferredPromise<void>();
@@ -185,6 +185,10 @@ test("fetch: dispatches close events on client and server close", async (t) => {
 	await serverSideClose(true);
 	await serverClosePromise;
 });
+test(
+	"fetch: dispatches close events on client and server close",
+	fetchDispatchCloseFlakyTest
+);
 test("fetch: throws on ws(s) protocols", async (t) => {
 	await t.throwsAsync(
 		fetch("ws://localhost/", {

packages/miniflare/test/test-shared/asserts.ts

@@ -1,5 +1,6 @@
 import assert from "assert";
 import { ExecutionContext } from "ava";
+import { Awaitable } from "miniflare";
 
 export function isWithin(
 	t: ExecutionContext,
@@ -21,3 +22,22 @@ export function escapeRegexp(value: string): RegExp {
 	// From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_expressions#escaping
 	return new RegExp(value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"));
 }
+
+export function flaky(
+	impl: (t: ExecutionContext) => Awaitable<void>
+): (t: ExecutionContext) => Promise<void> {
+	const maxAttempts = 3;
+	return async (t) => {
+		for (let attempt = 1; attempt <= maxAttempts; attempt++) {
+			const result = await t.try(impl);
+			if (result.passed || attempt === maxAttempts) {
+				result.commit();
+				return;
+			} else {
+				result.discard();
+				t.log(`Attempt #${attempt} failed!`);
+				t.log(...result.errors);
+			}
+		}
+	};
+}