[Bug]: `document` is `null` during microtasks at the end of a test

[eps1lon]

Version

27.5.1

Steps to reproduce

1. clone https://github.com/eps1lon/react-testing-library-error-repro/tree/jest-repro
2. checkout jest-repro branch
3. yarn install
4. yarn test

Expected behavior

Test fails due to timeout.

Actual behavior

document is null during a microtask scheduled from a ReactDOMTestUtils.act call.

Additional context

Continued from #9056 (comment) which is a reduced repro of testing-library/react-testing-library#1027

Environment

System:
    OS: Linux 5.13 Ubuntu 20.04.4 LTS (Focal Fossa)
    CPU: (16) x64 Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz
  Binaries:
    Node: 14.18.3 - ~/.nvm/versions/node/v14.18.3/bin/node
    Yarn: 1.22.17 - ~/.nvm/versions/node/v14.18.3/bin/yarn
    npm: 6.14.15 - ~/.nvm/versions/node/v14.18.3/bin/npm
  npmPackages:
    jest: ^27.5.1 => 27.5.1

[thebrianbug]

This error is difficult for non-react savvy folks to understand. It would be great to fix the issue and add more error messaging to direct folks on what to do about it a bit more clearly.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[eps1lon]

comment

[edishu]

As discussed in testing-library/react-testing-library#1027. This issue is experienced very often while running async tests on Github Actions CI. As a mitigation I add jest.runAllTimers() at the end of test to exhaust all micro/macro task queues, but it rarely works.

Also, I have tests which run successfully on local machine but fail only in Github Actions CI with:

      var evt = document.createEvent('Event');

[johachi]

I have been able to consistently reproduce this error on my local machine. But to do that I have to do yarn test --runInBand while also putting my machine under a heavy workload (e.g. playing a few youtube videos on the highest resolution or screen share). Still no luck in finding the culprit. 😭

[Zylphrex]

I ended up patching react-dom in my node_modules locally and added some debugging code to identify the problematic test. You can see it at https://github.com/Zylphrex/react-testing-library-error-repro. It's a little gross but I hope it helps.

[johachi]

I ended up patching react-dom in my node_modules locally and added some debugging code to identify the problematic test. You can see it at https://github.com/Zylphrex/react-testing-library-error-repro. It's a little gross but I hope it helps.

This worked excellently well! 🎉 Thank you so much @Zylphrex !

It did point me to the test and place I thought was probably the culprit. I still can't figure out why it is failing though. But I can solve the problem by adding a longer timeout for the test that is failing but it is not a solution I'm satisfied with.

[mjchang]

After trying random things to solve this issue, I discovered that increasing test timeout (jest.setTimeout, 30000) or test('title', () => {...}, 30000)) fixed it for me. Disclaimer - I don't fully understand how this helped and whether this is reliable. Would appreciate an explanation if this is the proper workaround 🙏

[Zylphrex]

@mjchang If you were facing the same problem, that should fix it.

The root cause of this problem when I initially opened up testing-library/react-testing-library#1027 was that the test timed out during one of the getBy* queries. Your choices here are to increase the timeouts or make your test run faster.

I believe what's happening here is because the test had timed out, jest started to do tear downs (I'm not sure exactly what). And at some point after, the getBy* tries to poll for results again and encounters this particular error which is not helpful in determining what the actual problem was.