`requestAnimationFrame` callbacks are never called with legacy fake timers when advancing time

[eps1lon]

🐛 Bug Report

Callbacks scheduled with requestAnimationFrame are not called when using jest.useFakeTimers('legacy') and jest.advanceTimersByTime(17)

To Reproduce

test.each(["legacy", "modern"])(
  "%s fake timers wait for requestAnimationFrame",
  async (timerImplementation) => {
    jest.useFakeTimers(timerImplementation);
    let exited = false;
    // implemented in JSDOm with `setInterval(callback, 16.6666)`
    requestAnimationFrame(() => {
      exited = true;
    });

    jest.advanceTimersByTime(15);

    expect(exited).toBe(false);

    jest.advanceTimersByTime(2);

    expect(exited).toBe(true);
  }
);

Expected behavior

Tests pass with legacy and modern fake timers

Link to repl or repo (highly encouraged)

https://github.com/eps1lon/jest-fake-timers-request-animation-frame

envinfo

  System:
    OS: Linux 5.4 Ubuntu 20.04.2 LTS (Focal Fossa)
    CPU: (6) x64 Intel(R) Core(TM) i5-9400 CPU @ 2.90GHz
  Binaries:
    Node: 12.22.1 - ~/.nvm/versions/node/v12.22.1/bin/node
    Yarn: 1.22.5 - /usr/bin/yarn
    npm: 6.14.12 - ~/.nvm/versions/node/v12.22.1/bin/npm
  npmPackages:
    jest: ^27.0.4 => 27.0.4

[SimenB]

Legacy timers do not support rAF: https://github.com/facebook/jest/blob/d1882f2e6033186bd310240add41ffe50c2a9259/packages/jest-fake-timers/src/legacyFakeTimers.ts#L31-L40 (and jsdom uses its own setInterval, not the one exposed, so mocking one doesn't mock the other)

PR welcome!

[eps1lon]

Thanks for the quick response.

Legacy timers do not support rAF:

I'm not sure why waitFor from @testing-library/dom was working before we merged testing-library/dom-testing-library#966 though. Maybe it just worked incidentally because we used to real setImmediate which would flush animation frames at some point (even though the timing would be completely off).

PR welcome!

Let me check if I can throw something together quickly. Not sure if this will be useful though since that would still require updating jest itself.

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