fakeSchedulers stopped working with rxjs 7

[Christian Kircheis]

I recently upgraded rxjs and rxjs-marbles to v7 in a stencil project.
This caused some jest tests using fakeSchedulers to test debounceTime to stop working.

I don't know if this is a bug, or an error on my side, but any help would be really appreciated.

I created a repo that reproduces this https://github.com/thccorni/rxjs-marbles-fake-schedulers-with-rxjs-7

To summarize:
I have some component emitting user input after some debounce time.

this.countDebouncer$
  .pipe(debounceTime(this.dueTime), takeUntil(this.destroy$))
  .subscribe((count) => {
    this.countChange.emit(count);
    console.log('emitting', { count });
  });

// some click handler
this.countDebouncer$.next(count)

I usually tested this using advance with the appropriate amount of time, which worked great until now

fakeSchedulers(async (advance) => {
  // omitted…
  button.click();
  expect(emit).not.toBeCalled();
  advance(300);
  expect(emit).toBeCalledTimes(1);
}),

Thanks for your help in advance!

[Nicholas Jamieson]

fakeSchedulers most likely won't work with an async function because, AFAICT, as soon as the function returns - it'll return a promise - the scheduler patching/faking will be restored, so anything that happens with schedulers after an await will be dealing with unpatched, no-longer-faked schedulers.

It could be made to work with an async function, but ATM it won't and it never has in the past.

[Christian Kircheis]

Thanks a lot for clarification. I could solve my problem by moving the async stuff before running fakeSchedulers.