not understanding how to test subscription side effects #566

  @select() theme$: Observable<IAppTheme>;
  theme: IAppTheme;

  constructor(public overlay: OverlayContainer,
              public acts: Actions) {
    this.theme$.subscribe((theme: IAppTheme) => {
      this.setTheme(theme.product.name); // this function changes a bunch of css based on the theme and uses the theme name to call the right css classes
      this.theme = theme; // this makes it easier and a lot less ugly in the html then using | async everywhere
    });
  }

  ngOnInit(): void {
    this.acts.installTheme(this.theme); // this is an Action that updates the theme,  it is there because its annoying to switch themes to see changes every time I made changes to them.
  }

  beforeEach(() => {
    fixture = TestBed.createComponent(AppComponent);
    router = TestBed.get(Router);
    component = fixture.componentInstance;
    redux = TestBed.get(NgRedux);
    de = fixture.debugElement;

    fixture.detectChanges();
  });

  it('should update theme through subscription in init', fakeAsync(() => {
    expect(component.theme).toBeUndefined(); // passes
    component.ngOnInit();
    fixture.detectChanges();
    flushMicrotasks();
    fixture.whenStable().then(() =>
      expect(component.theme).toBeUndefined(); // passes but not what I want
      // expect(component.theme.name).toBe('default'); // what I want to pass
    );
  }));