How do I test Components & Routing with the RouterTestingHarness 

Yes, it also works with nested components. Do you have an example for your issue. Sounds like this should not happen. You can try out this code. @Component({ template: ``, imports: [RouterOutlet], standalone: true, }) class MiddleComponent { constructor() { console.log('hallo'); } } describe('Detail Component', () => { it('should test verify the id is 5', waitForAsync(async () => { TestBed.configureTestingModule({ providers: [ provideRouter([ { path: 'detail', component: MiddleComponent, children: [{ path: ':id', component: DetailComponent }], }, ]), ], }); const harness = await RouterTestingHarness.create('detail/5'); const p: HTMLParagraphElement = harness.fixture.debugElement.query( By.css('p'), ).nativeElement; expect(p.textContent).toBe('Current Id: 5'); await harness.navigateByUrl('/detail/6'); expect(p.textContent).toBe('Current Id: 6'); })); });

Exactly!