Flaky test requires delay: null to prevent Exceeded timeout of 5000 ms for a test only on CircleCI even though we're not using fake timers

[joshunger]

Good afternoon!

We upgraded to 14.4.3 and all tests work locally. When run on CircleCI, we have one test that throws a Exceeded timeout of 5000 ms even though we not using fake timers in this test file.

Adding delay: null fixed the issue. Also advanceTimers: jest.advanceTimersByTime fixes the issue but produces the warning -

A function to advance timers was called but the timers API is not mocked with fake timers. Call `jest.useFakeTimers()` in this test or enable fake timers globally by setting `"timers": "fake"` in the configuration file

How would I debug into this issue?

Any help would be greatly appreciated. 🙏