Angular如何测试组件中EventEmitter的订阅

Question

我的组件中有以下订阅：

finishLanguageChange 在我的一项服务中是 EventEmitter

  ngOnInit(): void {
    // Update dates on Language change
    this.refs.translateRef = 
      this.languageManagerService.finishLanguageChange.subscribe((event) => {
      this.langCode = this.languageManagerService.getLangCode();
      this.cdRef.detectChanges();
    });
  }

并且我想返回该订阅的值以测试代码。

我试试这个，但不幸的是，它需要返回订阅类型，我不知道该怎么做

  it('Check Date config', async(() => {
    spyOn(languageManagerService.finishLanguageChange, 'subscribe').and.returnValue(true);
     fixture.detectChanges();

    expect(component.langCode)..toBeTruthy();
  }));

Answer 1

您应该创建服务的模拟间谍对象。

let languageManagerServiceSpy: jasmine.SpyObj<LanguageManagerService>;

beforeEach(() => {
  const spy = 
  TestBed.configureTestingModule({
    // Provide spy dependency
    providers: [
      // other providers
      { provide: LanguageManagerService, useValue: jasmine.createSpyObj('LanguageManagerService', ['finishLanguageChange', 'getLangCode'])}
    ]
  });

  // Inject spy dependency
  languageManagerServiceSpy = TestBed.inject(LanguageManagerService) as jasmine.SpyObj<LanguageManagerService>;
});

测试用例：

it('Check Date config', () => {
    
  languageManagerServiceSpy.finishLanguageChange.and.returnValue(of("test"));
    languageManagerServiceSpy.getLangCode.and.returnValue("test");
     fixture.detectChanges();

    expect(component.langCode)..toBeTruthy();
});