feat: expose schedule() method

[MillerSvt]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[just-jeb]

Hey, could you please elaborate on the use case that you want to test?

[MillerSvt]

Sure. Here is abstract example, but it is often found in our tests.

class EffectsService {
    showSuccessStateEffect$ = createEffect(() => this.actions$.pipe(
        ofType(showSuccessState),
        // ignore all events while message is visible
        exhaustMap(() => merge(
            // show success message for three seconds
            of(true),
            timer(timeout).pipe(map(() => false)),
        ),
    ));
}

We need to test these cases. First case is simple for test:

actions$ = new ReplaySubject(1);
actions$.next(showSuccessState());

const expected = cold('t-----f', {
    t: true,
    f: false,
});

expect(effects.showSuccessStateEffect$).toBeObservable(expected);

But how can we test whether events are being ignored?

actions$ = new ReplaySubject(1);
actions$.next(showSuccessState());

cold('---a|').subscribe(() => actions$.next(showSuccessState()));

const expected = cold('t-----f------', {
    t: true,
    f: false,
});

expect(effects.showSuccessStateEffect$).toBeObservable(expected);

But as for me, it looks ugly. It is better to use schedule() function:

actions$ = new Subject();

schedule(() => actions$.next(showSuccessState()), 2);
schedule(() => actions$.next(showSuccessState()), 4);
schedule(() => actions$.next(showSuccessState()), 11);

const expected = cold('-t-----f--t-----f---', {
    t: true,
    f: false,
});

expect(effects.showSuccessStateEffect$).toBeObservable(expected);

As I mentioned earlier, this is a hypothetical scenario. In our tests, we mock the actions$ using TestBed in the beforeEach block. Therefore, we cannot use the cold() function for actions$, as it may vary depending on the specific test case. And our effects are more complex, so we need to perform side effects more often.

[just-jeb]

Both your PRs have been released in 3.1.0.