模拟要在 Angular 单元测试中订阅的模拟服务的主题 属性

Question

在我的 Angular 单元测试中，我的模拟服务有两个属性：

  public messageChange: Subject<ChatMessage> = new Subject<ChatMessage>();
  public gameChange: Subject<GameState> = new Subject<GameState>();

在我的 SUT 中，我在我的构造函数中使用它们：

this._subChat = this.hub.messageChange.subscribe((message: ChatMessage) => {
      this.message = message;
      this.messageChange.next(this.message);
    });
    this._subGame = this.hub.gameChange.subscribe((game: GameState) => {
      this.game.setGame(game);
    });

现在我正在尝试使用这两种方法来模拟来自模拟服务的属性：

• How to spyOn a value property (rather than a method) with Jasmine

现在我的测试是这样的：

describe('SignalRService', () => {
  let signalrService: SignalRService;
  const hubServiceMock = jasmine.createSpyObj('HubConnectionService', [
    'isConnectionStarted',
  ]);
  const messageChange = new Subject();
  const gameChange = new Subject();

  beforeEach(() => {
    signalrService = new SignalRService(
      hubServiceMock
    );
    let msg = {} as ChatMessage;
    let gam = {} as GameState;
    messageChange.next(msg);
    gameChange.next(gam);
  });

  it('Service_ShouldBeCreated', () => {
    spyOnProperty(hubServiceMock, 'messageChange', 'get').and.returnValue(
      messageChange
    );
    spyOnProperty(hubServiceMock, 'gameChange', 'get').and.returnValue(
      gameChange
    );
    expect(signalrService).toBeTruthy();
  });
}

所以在我创建的测试中：

• 服务模拟 hubServiceMock,

• 假messageChange = new Subject();,

• 假gameChange = new Subject();,

• i 运行 .next,

• 并且我为属性设置了间谍：

  spyOnProperty(hubServiceMock, 'messageChange', 'get').and.returnValue( messageChange );

  spyOnProperty(hubServiceMock, 'gameChange', 'get').and.returnValue( gameChange );

为什么对我不起作用？我收到一个错误：

Cannot read property 'subscribe' of undefined

Answer 1

它不起作用，因为 hubServiceMock 在其 messageChange 和 gameChange 中没有假主题，您需要在调用 new SignalRService(hubServiceMock) 之前设置它们。

  const hubServiceMock = jasmine.createSpyObj('HubConnectionService', [
    'isConnectionStarted',
  ]);
  const messageChange = new Subject();
  const gameChange = new Subject();

  // add this
  hubServiceMock.messageChange = messageChange;
  hubServiceMock.gameChange = gameChange;

那么它应该可以工作，也许需要进行一些小的调整。

---

我建议在这种情况下使用模拟库以避免痛苦。

例如 ng-mocks，测试可能如下所示：

describe('SignalRService', () => {
  beforeEach(() => MockBuilder(SignalRService, ITS_MODULE));

  const hubServiceMock = {
    messageChange: new Subject(),
    gameChange: new Subject(),
  };
  beforeEach(() => MockInstance(HubConnectionService, hubServiceMock));


  it('Service_ShouldBeCreated', () => {
    const signalrService = MockRender(SignalRService).point.componentInstance;
    expect(signalrService).toBeTruthy();

    hubServiceMock.messageChange.next({});
    hubServiceMock.gameChange.next({});
    // next assertions.
  });
}

Answer 2

我最终采用了一种方法，我像这样注入模拟服务：

hubServiceMock = TestBed.inject(HubConnectionService);

然后我这样嘲笑我的 Subjects:

it('Service_ShouldBeCreated', () => {
    spyOn(hubServiceMock.messageChange, 'next');
    spyOn(hubServiceMock.gameChange, 'next');
    expect(signalrService).toBeTruthy();
  });

在其他测试中，我可以使用这样的模拟服务方法：

let spyIsConnectionStarted = spyOn(hubServiceMock, 'isConnectionStarted');
    spyIsConnectionStarted.and.returnValue(true);