javascript - karma : Cannot read property * of undefined

Question

我有一个我想测试的服务:

@Injectable()
export class AuthenticationService {
  initialAuthStatus = this.authenticationStatus.first();

  constructor(private adalService: AdalService,
              private settingsProvider: SettingsProvider) { }


  public get authenticationStatus(): any {
    return this.adalService.userInfo.authenticationStatus;
  }
}

以及服务测试:

describe('AuthenticationService', () => {
    let mockAdalService: any;
    let adalService: any;
    let service: any;
    let mockSettingsProvider: any;
    beforeEach(() => {
        TestBed.configureTestingModule({
          providers: [
            AuthenticationService, 
            AdalService,
            { provide: SettingsProvider, useClass: MockSettingsProvider },
            { provide: AdalService, useClass: MockAdalService }
          ]
        });

        mockAdalService = new MockAdalService();
        adalService = new AdalService();
        mockSettingsProvider = new MockSettingsProvider();
    });

    it('should be created', inject([AuthenticationService], (service: AuthenticationService) => {
        expect(service).toBeTruthy();
    }));
});

但是，测试失败并显示以下错误消息:

AuthenticationService should be created
TypeError: Cannot read property 'authenticationStatus' of undefined

跟认证状态的getter有关系，但是我想不通到底为什么会失败。

非常感谢任何帮助:)

Answer 1

在类的顶部，在这一行中，声明类属性 initialAuthStatus:

initialAuthStatus = this.authenticationStatus.first();

this.authenticationStatus 还没有初始化，给你错误信息。为了让它工作，将该行放在 ngOnInit() 方法中并将纯声明部分保留在类的顶部。

initialAuthStatus;
...
ngOnInit(){
    this.initialAuthStatus = this.authenticationStatus;
}
...
...