提供服务的组件的 Angular 2 测试规范 [英] Angular 2 test spec for a component that provides a service

问题描述

我正在使用 Angular 2 final (2.0.1).我有一个提供服务的组件.它是唯一使用它的，这就是为什么它提供它而不是包含模块并且它也被注入到构造函数中.

I am using Angular 2 final (2.0.1). I have a component that provides a service. It is the only one that uses it, this is why it provides it and not the containing module and it is also being injected into the constructor.

@Component({
    selector: 'my-comp',
    templateUrl: 'my-comp.component.html',
    styleUrls: ['my-comp.component.scss'],
    providers: [MyService],
})
export class MyComponent {

    constructor(private myService: MyService) {
    }
}

当我尝试实现规范时，它失败了.

When I try to implement the spec, it fails.

describe("My Component", () => {

beforeEach(() => {
    TestBed.configureTestingModule({
        declarations: [MyComponent],
        providers: [
            {
                provide: MyService,
                useClass: MockMyService
            },
        ]
    });

    this.fixture = TestBed.createComponent(MyComponent);
    this.myService = this.fixture.debugElement.injector.get(MyService);

});

describe("this should pass", () => {

    beforeEach(() => {
        this.myService.data = [];
        this.fixture.detectChanges();
    });

    it("should display", () => {
        expect(this.fixture.nativeElement.innerText).toContain("Health");
    });

});

但是，当我将服务提供声明从组件移动到包含模块时，测试通过了.

but, when I move the service provide declaration from the component to the containing module, the tests passes.

我认为这是因为 TestBed 测试模块定义了模拟服务，但是在创建组件时 - 它用实际实现覆盖了模拟...

I assume it is because the TestBed testing module defines the mock service, but when the component is created - it overrides the mock with the actual implementation...

有人知道如何测试提供服务的组件并使用模拟服务吗?

Does anyone have any idea how to test a component that provides a service and use a mock service?

推荐答案

您需要覆盖 @Component.providers，因为它优先于您通过测试台配置提供的任何模拟.

You need to override the @Component.providers, as it has precedence over any mock you provide through the test bed config.

beforeEach(() => {
  TestBed.configureTestingModule({
    declarations: [MyComponent]
  });

  TestBed.overrideComponent(MyComponent, {
    set: {
      providers: [
        { provide: MyService, useClass: MockMyService }
      ]
    }
  }); 
});

另请参阅:

• 覆盖组件提供者

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