check variable after service call in angular testing script

ahanaService is service, tenantList is component variable and getTenantLists is service method

it('should have as all tenant list', fakeAsync(() => {
    const fixture = TestBed.createComponent(AppComponent);
    const comp = fixture.debugElement.componentInstance;
    spyOn(comp['ahanaService'], 'getTenantLists').and.callThrough();
    comp.ngOnInit();
    tick();
    expect(comp['tenantList']).not.toBe(null);
  }));