Question

我第一次使用Karma / Jasmine等来测试我的一个组件，并且主要跟随docs on testing。我的组件需要3个构造函数参数;

constructor(
  private myService: MyService,
  private renderer: Renderer,
  private element: ElementRef
) { }

我试图模拟/存储基于this section of the docs的依赖关系，如下所示;

// Mocks/Stubs
const myServiceStub = {};
class MockElementRef {}
class MockRenderer {}

// beforeEach block
beforeEach(() => {
  TestBed.configureTestingModule({
    declarations: [ MyComponent ],
    providers: [
      { provide: ElementRef, useClass: MockElementRef },
    { provide: Renderer, useClass: MockRenderer },
      { provide: MyService, useValue: myServiceStub},
    ]
  });

  fixture = TestBed.createComponent(MyComponent);
});

尽管如此，每当我运行测试时，我都会收到以下错误;

Error: Can't resolve all parameters for MyComponent: (?, ?, ?).
    at SyntaxError.ZoneAwareError (test.ts:9250:33)
    at SyntaxError.BaseError [as constructor] (test.ts:44243:16)
    at new SyntaxError (test.ts:44453:16)
    at CompileMetadataResolver._getDependenciesMetadata (test.ts:61503:31)

我在这里缺少什么？谢谢！

Answer 1

它可以由循环DI引起，尝试重构你的组件MyComponent以注入这样的服务：

constructor(@Inject(forwardRef(() => MyComponentService)) private myService: MyComponentService) {}

Angular2组件测试 - 错误：无法解析所有参数

1 个答案: