如何仅对一个测试覆盖Angular 5中的Provider? [英] How override Provider in Angular 5 for only one test?

问题描述

在我的一个单元测试文件中，我不得不使用不同的模拟对同一服务进行多次模拟.

In one of my unit test files, I have to mock several times the same service with different mocks.

import { MyService } from '../services/myservice.service';
import { MockMyService1 } from '../mocks/mockmyservice1';
import { MockMyService2 } from '../mocks/mockmyservice2';
describe('MyComponent', () => {

    beforeEach(async(() => {
        TestBed.configureTestingModule({
        declarations: [
            MyComponent
        ],
        providers: [
            { provide: MyService, useClass: MockMyService1 }
        ]
        })
        .compileComponents();
    }));

    beforeEach(() => {
        fixture = TestBed.createComponent(MapComponent);
        mapComponent = fixture.componentInstance;
        fixture.detectChanges();
    });

    describe('MyFirstTest', () => {
        it('should test with my first mock', () => {
            /**
             * Test with my first mock
             */
        });
    });

    describe('MySecondTest', () => {
        // Here I would like to change { provide: MyService, useClass: MockMyService1 } to { provide: MyService, useClass: MockMyService2 }

        it('should test with my second mock', () => {
            /**
             * Test with my second mock
             */
        });
    });
});

我看到函数 overrideProvider 存在，但是我没有设法在我的测试中使用它.当我在"it"中使用它时，提供程序不会更改.我没有找到一个调用此函数的示例.您能解释一下如何正确使用它吗?还是您有其他方法可以做到这一点?

I see that the function overrideProvider exists, but I did not manage to use it in my test. When I use it in a "it", the provider doesn't change. I didn't manage to find an example where this function is called. Could you explain me how to use it properly? Or have you an other method to do that?

推荐答案

如果服务是作为公共属性注入的，例如:

If the service is injected as public property, e.g.:

@Component(...)
class MyComponent {
  constructor(public myService: MyService)
}

您可以执行以下操作:

it('...', () => {
  component.myService = new MockMyService2(...); // Make sure to provide MockMyService2 dependencies in constructor, if it has any.
  fixture.detectChanges();

  // Your test here...
})

如果注入的服务存储在私有属性中，则可以将其写为(component as any).myServiceMockMyService2 = new MockMyService2(...);来绕过TS.

If injected service is stored in a private property, you can write it as (component as any).myServiceMockMyService2 = new MockMyService2(...); to bypass TS.

虽然不漂亮，但是可以.

It's not pretty but it works.

对于TestBed.overrideProvider，我对这种方法没有运气(如果可行的话会更好):

As for TestBed.overrideProvider, I had no luck with that approach (which would be much nicer if it worked):

it('...', () =>{
  TestBed.overrideProvider(MyService, { useClass: MockMyService2 });
  TestBed.compileComponents();
  fixture = TestBed.createComponent(ConfirmationModalComponent);
  component = fixture.componentInstance;
  fixture.detectChanges();

  // This was still using the original service, not sure what is wrong here.
});

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