unit-testing – 使用本机视图封装时访问嵌套组件的DebugElement

@Component({
  selector: 'my-component',
  template: `
    <my-nested-component [state]="state"></my-nested-component>
  `,
  encapsulation: ViewEncapsulation.Native
})
export class MyComponent {}

单元测试我的组件时,我想获得对嵌套组件MyOtherComponent的引用.如果我的组件没有使用封装,或者它使用了模拟封装,我可以使用：

let fixture = TestBed.createComponent(MyComponent);
let nestedComponent = fixture.debugElement.query(By.directive(MyNestedComponent))

获取对组件的引用.

但在这种情况下,查询只是查询组件的轻DOM子项(模仿querySelector的行为),因此当使用本机视图封装时,nestedComponent为null.

你应该如何获得嵌套组件的DebugElement(以及组件实例)的引用？

@Component({
  selector: 'my-nested-component',
  template: `
    <h1>Nested component - {{ state }}</h1> 
  `,
})
export class NesterComponent {
  @Input() state: number;
}

@Component({
  selector: 'my-app',
  template: `
    <my-nested-component [state]="state"></my-nested-component> 
  `,
  encapsulation: ViewEncapsulation.Native
})
export class TestComponent {
  state = 1;
}

所以我会写这样的测试：

let fixture = TestBed.createComponent(TestComponent);
let component = fixture.componentInstance;

const shadowRoot: DocumentFragment = fixture.debugElement.nativeElement.shadowRoot;
const nestedComponentNativeElement = shadowRoot.querySelector('my-nested-component');

const nestedComponentDebugElement = <DebugElement>getDebugNode(nestedComponentNativeElement);

var nestedComponentInstance: NesterComponent = nestedComponentDebugElement.componentInstance;
// here can be your code

component.state = 2;
fixture.detectChanges();

de = nestedComponentDebugElement.query(By.css('h1'));

expect(de.nativeElement.textContent).toBe('Nested component - 2');

你也可以尝试这个测试作为一个live example in plunker