Type Error: Cannot read property 'next' of undefined in Angular/Jasmine

Question

当我在组件中使用以下服务时，显示错误"TypeError: Cannot read property 'next' of undefined"，之前没有引起任何问题的测试也失败了。

服务：

  export class DataService {

  loadData$: Observable<string>;
  observerLoadData: Observer<string>;
  constructor() {
    this.loadData$ = new Observable(observer => this.observerLoadData = observer);
    this.startObs();
  }

  startObs() {
    setTimeout(() => {
      this.observerLoadData.next('LOADEDDATA$');
      console.log('huhu');
    }, 2500); }
}

组件：

  ....
  constructor(private dataService: DataService) {
       this.dataService.loadData$.subscribe(value => this.loadedData = value);
  }
  ....

规格：

....
beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [
        AppComponent
      ],
      providers: [] 
      ,
      imports: [
        BrowserModule,
        FormsModule,
        ReactiveFormsModule
      ]

    }).compileComponents().then(() => {
      fixture = TestBed.createComponent(AppComponent);
      comp = fixture.componentInstance;
      de = fixture.debugElement.query( By.css('form') );
      el = de.nativeElement;
    });
....

Answer 1

您需要在测试中提供DataService给。

providers: [
  {
    provide: DataService,
    useValue: {
      loadData$: of('VALUE_OF_LOADED_DATA'),
    },
  },
],

Type Error: Cannot read property 'next' of undefined in Angular/Jasmine

Type Error: Cannot read property 'next' of undefined in Angular/Jasmine

service

typeerror

jasmine

karma-runner

angular