waitFor not working when vi.useFakeTimers is used

[jonaskuske]

When vi.useFakeTimers is used in a test, waitFor does not longer run change detection.

it('works', async () => {
  vi.useFakeTimers()
  const view = await render(MyComponent)
  view.detectChanges()
  expect(screen.getByRole('input').toHaveAccessibleDescription(/something/))
})

it('does not work', async () => {
  vi.useFakeTimers()
  await render(MyComponent)
  await waitFor(() => expect(screen.getByRole('input').toHaveAccessibleDescription(/something/)))
})

It only happens when using Vitest, not when using Jest. (in fact, globalThis.jest = vi in the setup script suffices as workaround for some reason)

The cause appears to be the use of setTimeout in the waitForWrapper: https://github.com/testing-library/angular-testing-library/blob/main/projects/testing-library/src/lib/testing-library.ts#L592

The problem disappears when I replace

    setTimeout(() => detectChanges(), 0);

with

    Promise.resolve().then(() => detectChanges());

I assume that waitFor itself is using the fake setTimeout and thus never runs, waiting for the time to advance.