即使已提到新的提供程序，也应按角度插入真实服务而不是模拟服务

Question

我正在观察一种奇怪的行为。我有一个使用QuestionManagementService的组件，并希望在规格中使用其模拟，但是Angular会同时创建真实和模拟服务！

我的组件使用QuestionManagementService

constructor(..., private questionManagementService: QuestionManagementService,...) {
          /*
    In spec, this prints QuestionManagementService instead of MockQuestionManagementService!!!!        
    */    
console.log('question mgmt in constructor ',questionManagementService);
        this.supportedTags=new SupportedTags([]);
      }

ngOnInit(){
....
let subscription = this.questionManagementService.getSupportedTags(this.tagId);//remove hardcoding.
}

要对组件进行单元测试，我创建了QuestionManagementService

的模型

class MockQuestionManagementService{
  questionsArray$: Observable<Result>;
  question$: Observable<Result>;
  tags$:Observable<Result>;
  addQuestion$:Observable<Result>;

  questionsArraySubject: BehaviorSubject<Result>; //to send list of questions
  questionSubject: BehaviorSubject<Result>; //to send details of a question
  tagsSubject: BehaviorSubject<Result>; //to send details of a question
  addQuestionSubject:BehaviorSubject<Result>;

  getSupportedTags(tagId:TagId):any {
    console.log("In mock QuestionManagementService: getSupportedTags: ",tagId);
    let tag1 = new Tag('c1','s1','t1');
    let tag2 = new Tag('c2','s2','t2');
    let tag3 = new Tag('c3','s3','t3');
    let tags:Tag[] = [tag1,tag2,tag3];
    let supportedTags = new SupportedTags(tags);
    this.tagsSubject.next(new Result('success',supportedTags));
  }

  constructor(){
/*You'll see in the image the first question management service is created, then this one!!!
*/
    console.log("created mock service");
    this.questionsArraySubject = new BehaviorSubject<Result>(new Result('initial',{})); //A Subject can act both as an Observable and an Observer
    this.questionSubject = new BehaviorSubject<Result>(new Result('initial',{}));
    this.tagsSubject = new BehaviorSubject<Result>(new Result('initial',{}));
    this.addQuestionSubject = new BehaviorSubject<Result>(new Result('initial',{}));
    this.questionsArray$ = this.questionsArraySubject.asObservable(); //create Observable. Other components can subcribe to it now to get notifications/values
    this.question$ = this.questionSubject.asObservable(); //create Observable. Other components can subcribe to it now to get notifications/values
    this.tags$ = this.tagsSubject.asObservable();
    this.addQuestion$ = this.addQuestionSubject.asObservable();

  }

}

，并提到要在providers

中使用它

describe('NewPracticeQuestionComponent', () => {
  let component: NewPracticeQuestionComponent;
  let fixture: ComponentFixture<NewPracticeQuestionComponent>;
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ NewPracticeQuestionComponent,
      DialogBoxComponent,
        ShowErrorsComponent],
      imports:[ReactiveFormsModule,HttpClientTestingModule],
      providers:[WebToBackendInterfaceService,
        HelperService,
        AuthService,
        {provide: QuestionManagementService, useClass:MockQuestionManagementService}] //QuestionManagementService is being created even though I have mentioned a different class
    })

 TestBed.overrideModule(BrowserDynamicTestingModule, {
      set: {
        entryComponents: [DialogBoxComponent]/*DialogBoxComponent is created dynamically (imperatively), soit nee to be ddded in entryComponent*/
      }
    })
    .compileComponents();

然后我得到了规范中的服务实例

fit('should get tags from the server on loading',()=>{
    let newPracticeQuestionComponent = component;
    let questionManagementService = TestBed.get(QuestionManagementService);
    console.log('component is ',newPracticeQuestionComponent);
    console.log('service is ',questionManagementService);
    spyOn(questionManagementService,'getSupportedTags');
    expect(newPracticeQuestionComponent.supportedTags["supported-tags"].length).toBe(0);
    expect(questionManagementService.getSupportedTags).toHaveBeenCalledWith(newPracticeQuestionComponent.tagId);
    expect(newPracticeQuestionComponent.supportedTags["supported-tags"].length).toBe(3);

规范未能说明Expected spy getSupportedTags to have been called with [ TagId({ course: 'coding' }) ] but it was never called.，因为它是从getSupportedTags而不是QuestionManagementService调用MockQuestionManagementService的，所以我知道它正在发生。但是Angular为什么同时创建QuestionManagementService和MockQuestionManagementService？可能是因为TestBed.overrideModule做某件事很奇怪吗？