parallel/test-fs-promises-watch-iterator is flaky

[gurgunday]

Test

test-fs-promises-watch-iterator

Platform

macOS x64

Console output

Error: Command: out/Release/node --test-reporter=./test/common/test-error-reporter.js --test-reporter-destination=stdout /Users/runner/work/node/node/node/test/parallel/test-fs-promises-watch-iterator.js
--- TIMEOUT ---
make[1]: *** [test-ci] Error 1
make: *** [run-ci] Error 2

===
=== 1 tests failed
===

Build links

• N/A (CI is running macOS 15.6.1)
• https://github.com/nodejs/node/actions/runs/18065389437/job/51407387084?pr=60031

Additional information

No response

[lpinca]

I can reproduce the issue on my mac by running the following command:

python3 tools/test.py --repeat=1000 --timeout=2 test/parallel/test-fs-promises-watch-iterator.js

There seems to be a race condition where some (sometimes all) events are missing. If a small delay is added before writing the files the flakiness goes away

diff --git a/test/parallel/test-fs-promises-watch-iterator.js b/test/parallel/test-fs-promises-watch-iterator.js
index 1606bdef422..e73a1af589a 100644
--- a/test/parallel/test-fs-promises-watch-iterator.js
+++ b/test/parallel/test-fs-promises-watch-iterator.js
@@ -34,10 +34,10 @@ class WatchTestCase {
 }
 }
 async writeFiles() {
+ await setTimeout(common.platformTimeout(100));
 for (const fileName of [...this.files]) {
 await writeFile(this.filePath(fileName), Date.now() + fileName.repeat(1e4));
 }
- await setTimeout(common.platformTimeout(100));
 }
 }
 

Anyway, I'm not sure if the above patch invalidates the test or hides an actual bug in the watch/iterator implementation.

[gurgunday]

Anyway, I'm not sure if the above patch invalidates the test

Yeah I thought about moving the timeout up too but had the same concern

[pipobscure]

The test is meant to test that multiple file events are all handled when following in rapid succession. The sleep at the beginning is fine. As a matter of fact it should make things more stable as the the initial watcher setup is completed during that. The original test depends on asynchronous functions executing code before the first awai synchronously therefore staring the watcher before writing files.

So your instinct in moving the sleep up is good and we should do that. It won’t impact the test’s value so long as there is no sleep in between file writes.