Angular 使用组件ngOnInit时角度单元测试用例失败

我正在使用angular 7，在使用

component.ngOnInit（）

和

fixture.detectchanges（）

时无法运行单元测试用例。如果删除

component.ngOnInit（）

和

fixture.detectchanges（）

则测试用例通过，但我希望在spy之后检测更改

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [AppTestingModule, EffectsModule.forRoot([NodeEffects])],
      declarations: [SidenavComponent],
      schemas: [NO_ERRORS_SCHEMA],
      providers: [ApiNodesService]
    }).compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(SidenavComponent);
    component = fixture.componentInstance;
    browsingService = TestBed.get(BrowsingFilesService);
    apiNodesService = TestBed.get(ApiNodesService);
    appConfig = TestBed.get(AppConfigService);
    // appConfigSpy = spyOn(appConfig, 'get').and.returnValue([navItem]);
  });



  it('check getDocLibraries method is called', () => {
    spyOn(component, 'getDocLibraries');
    fixture.detectChanges();    
    component.ngOnInit();
    component.getDocLibraries();
    fixture.whenStable().then(data => {
      const debugUlElement = fixture.debugElement.query(By.css('ul.sidenav-menu_sub'));
      const nativeUlElement: HTMLUListElement = debugUlElement.nativeElement;
      expect(nativeUlElement.childElementCount).toEqual(1);
    });
  });
  });

错误消息：

TypeError:无法将未定义或null转换为对象
在Function.keys（）处
在SidenavComponent../src/app/components/sidenav/sidenav.component.ts.SidenavComponent.buildMenu(http://localhost:9876/src/app/components/sidenav/sidenav.component.ts?:93:19)
位于SidenavComponent../src/app/components/sidenav/sidenav.component.ts.SidenavComponent.ngonit(http://localhost:9876/src/app/components/sidenav/sidenav.component.ts?:76:28)
在UserContext。(http://localhost:9876/src/app/components/sidenav/sidenav.component.spec.ts?:103:15)

您应该将您的规范包装在

异步

中，并在稳定时将检测更改移到内部

  it('check getDocLibraries method is called', async(() => {
    spyOn(component, 'getDocLibraries');
    component.getDocLibraries();
    fixture.whenStable().then(()=> {
      fixture.detectChanges();
      const debugUlElement = fixture.debugElement.query(By.css('ul.sidenav-menu_sub'));
      const nativeUlElement: HTMLUListElement = debugUlElement.nativeElement;
      expect(nativeUlElement.childElementCount).toEqual(1);
    });
    component.ngOnInit();
  }));

注意：您有一个额外的'}）；'最后呢

您还可以使用fakeAsync&tick代替async&whenStable

  it('check getDocLibraries method is called', fakeAsync(() => {
    spyOn(component, 'getDocLibraries');
    component.getDocLibraries();
    component.ngOnInit();
    tick();
    fixture.detectChanges();
    const debugUlElement = fixture.debugElement.query(By.css('ul.sidenav-menu_sub'));
    const nativeUlElement: HTMLUListElement = debugUlElement.nativeElement;
    expect(nativeUlElement.childElementCount).toEqual(1);
  }));

---

尝试将“fixture.detectChanges（）”移到fixture.whenStable（）之前，可能会提供组件的代码？我已经添加了我收到的错误消息。