chore(cli-repl): add debugging info to async-repl tests (#2611)

The AsyncRepl tests have been flaky for a few runs on the waterfall now,
this should help try to figure out why specifically that is the case.

Author: addaleax

packages/cli-repl/src/async-repl.spec.ts

@@ -43,22 +43,35 @@ function createDefaultAsyncRepl(extraOpts: Partial<AsyncREPLOptions> = {}): {
 
 async function expectInStream(
   stream: Readable,
-  substring: string
+  substring: string,
+  timeoutMs: number | null = 5000
 ): Promise<void> {
   let content = '';
-  let found = false;
-  for await (const chunk of stream) {
-    content += chunk;
-    if (content.includes(substring)) {
-      found = true;
-      break;
-    }
+  let ended = false;
+  const result = await Promise.race([
+    (async () => {
+      for await (const chunk of stream) {
+        content += chunk;
+        if (content.includes(substring)) {
+          break;
+        }
+      }
+      ended = true;
+      return 'normal-completion' as const;
+    })(),
+    ...(timeoutMs ? [delay(timeoutMs).then(() => 'timeout' as const)] : []),
+  ]);
+  if (result === 'timeout') {
+    throw new Error(
+      `Timeout waiting for substring: ${substring}, found so far: ${content} (ended = ${ended})`
+    );
   }
-  expect(found).to.be.true;
+  expect(content).to.include(substring);
 }
 
 describe('AsyncRepl', function () {
   before(function () {
+    this.timeout(10000);
     // nyc adds its own SIGINT listener that annoys use here.
     process.removeAllListeners('SIGINT');
   });