testing modal dialogs with jasmine

my-test.component.spec.ts

// Create the test module
@NgModule({
  imports: [NgbModule.forRoot(), CommonModule],
  exports: [YesNoModalComponent, MyCustomComponent],
  declarations: [YesNoModalComponent, MyCustomComponent],
  entryComponents: [YesNoModalComponent]
})
class DialogTestModule { }

describe('MyTestComponent', () => {
  let component: PickDefinitionComponent;
  beforeEach(async(() => {
    TestBed.configureTestingModule({
        declarations: [MyTestComponent],
        providers: [ModalService], // ModalService includes the YesNoModalComponent
        imports: [NgbModule.forRoot(), DialogTestModule], // Import the test module
      })
        .compileComponents();
    }));
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(MyTestComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should call YesNoDialog', async () => {
    // Spy on the yesNoDialog     
    const modalService = TestBed.get(ModalService);
    const yesNoDialogSpy = spyOn(modalService, 'openYesNoDialog')
      .and.returnValue(new Promise<boolean>((resolve, reject) => {
          resolve(true);
    }));

    await component.showModal();

    await fixture.whenStable();
    await expect(yesNoDialogSpy).toHaveBeenCalled();
  });
});