如何替换@viewChildren 中用于测试替身的组件？

Question

假设我有一个要测试的组件，它使用了一个非常复杂的组件。此外，它使用 @viewChildren 获得的引用来调用它的一些方法。例如

    @Component({
        moduleId: module.id,
        selector: 'test',
        template: '<complex *ngFor='let v of vals'></complex>' ,
    })
    export class TestComponent{
    vals = [1,2,3,4]
    @ViewChildren(ComplexComponent) cpxs : QueryList<ComplexComponent>
    // ....
    }

如何在“TestBed”中替换测试替身的复杂组件？

类似

@Component({
  moduleId : module.id,
  selector: 'complex', template: ''
})
class ComplexComponentStub {
}

describe('TestComponent', () => {
  beforeEach( async(() => {
    TestBed.configureTestingModule({
      declarations : [ComplexComponentStub, TestComponent],
    });
it('should have four sons',()=>{
   let fixture = TestBed.createComponent(TestComponent);
   let comp    = fixture.componentInstance as TestComponent;
   fixture.detectChanges();
   expect(comp.cpxs.length).toBe(4);
});

    //....
}));

有关完整示例，请参阅 plnkr http://plnkr.co/edit/ybdrN8VimzktiDCTvhwe?p=preview

Answer 1

您可以使用反射元数据功能使其正常工作：

it('should have four sons', () => {
   const propMetadata = Reflect['getMetadata']('propMetadata', FatherComponent);
   var originType = propMetadata.cpxs[0].selector;
   propMetadata.cpxs[0].selector = ComplexComponentStub; // Replace ViewChild Type

   let fixture = TestBed.createComponent(FatherComponent);

   let comp = fixture.componentInstance as FatherComponent;
   fixture.detectChanges();
   expect(comp.cpxs.length).toBe(4);

   propMetadata.cpxs[0].selector = originType; // reset ViewChild
});

Test in Plunker

您可以在此处阅读有关装饰器和反射元数据的更多信息：

Angular 2, decorators and class inheritance

Answer 2

请注意，在 Angular 5 中，此解决方案似乎不再有效。然而 joshhunt 发现 (MyComponent as any)['prop__metadata'].child[0].selector = ChildDirectiveMock;应该可以，但感觉不是一个很好的永久解决方案。 – 乔什亨特

Answer 3

如果你只是想测试子组件中的函数是否被调用，你可以试试这个

component.ts

@ViewChildren('childComponent') childComponents: QueryList<YourComponent>;

component.spec.ts

  it('Your test name', () => {
    component.dashboard = dashboardMock; // ur using ngFor so u need to populate it first. u can mock it with ur own data
    fixture.detectChanges(); // component will render the ngfor
    const spies = [];
    component.childComponents.toArray().forEach((comp) => {
      comp.childFunction = () => { // Mock the function.
         return 'Child function called!';
      };
      const tempSpy = {
        spyKey: spyOn(comp, 'functionToBeMocked') // spy the mocked function
      };
      spies.push(tempSpy); // add to array
    });
    component.functionToTest(); // call the function u wish to test
    spies.forEach((spy) => { 
      expect(spy.spyKey).toHaveBeenCalled(); // check if child function are called
    });
  });

Answer 4

有关如何使用 Angular 10 解决此问题的讨论，请参阅 this question（因为此处描述的 none 技术超出了 Angular 9）。

如何替换@viewChildren 中用于测试替身的组件？

How to replace a component used in @viewChildren for a test double?

angular

angular2-directives

angular2-testing