Calling `ComponentFixture#detectChanges()` or `autoDetectChanges()` should re-trigger change detection after flushing effects about angular HOT 2 CLOSED

I actually misunderstood this before and it's working as expected today. The TL;DR is kind of that you're using autoDetect wrong in this case. You should be waiting for the fixture stableness rather than autoDetect to cause stableness to be applied synchronously. Using your test component above, this works:

 beforeEach(async () => {
    await TestBed.configureTestingModule({
      providers: [{provide: ComponentFixtureAutoDetect, useValue: true}]
    }).compileComponents();
  });

  it('should create the app', async () => {
   @Component({template: '{{title()}}'})
   class Example {
     title = signal('');
     constructor() {
       effect(() => {
         this.title.set('demo');
       }, {allowSignalWrites: true});
     }
   }
   
   const fixture = TestBed.createComponent(Example);
   await fixture.whenStable();
   expect(fixture.nativeElement.textContent).toEqual('demo'); // ✅
  });

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Thanks @atscott, I totally agree with you. ComponentFixture#whenStable() is indeed a way better option.

I think that my issue description was not very clear.
What I wanted to highlight is that there was a behavior change since the change of effect scheduling in v17.1.0 (1f8c53c)
Since effects became scheduled as microtasks, tests that relied on synchronous change detection using ComponentFixture#detectChanges were broken.

For example, Angular Testing Library currently relies on sync change detection instead of ComponentFixture#whenStable() (cf. https://github.com/testing-library/angular-testing-library/blob/main/projects/testing-library/src/lib/testing-library.ts#L253)
It would be wise to switch to whenStable() but then it raises another issue. There should be an opt-out when combined with fakeAsync as calling whenStable() with any pending timers in fakeAsync will produce the following error: timer(s) still in the queue. if we want to make assertions before flushing the timers.

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