unit-testing - 单元测试没有 ChangeDetectorRef 的提供者

Question

版本:Angular 4。

我正在将一个父组件注入(inject)到子组件中，以通过子组件访问父方法。

在父组件中，我不得不使用 ChangeDetectorRef，因为它有一个会更新运行时的属性。

现在代码工作正常，但子组件规范为注入(inject)父组件的“ChangeDetectorRef”抛出错误。

Error: No provider for ChangeDetectorRef!

父组件

import { Component, AfterViewChecked, ChangeDetectorRef, ChangeDetectionStrategy } from '@angular/core';

@Component({
  selector: 'parent-component',
  templateUrl: './parent.component.html',
  styleUrls: ['./parent.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class ParentComponent implements AfterViewChecked {

  stageWidth: number;

  constructor(private ref: ChangeDetectorRef) {
    this.ref = ref;
  }

  //call this function as many times as number of child components within parent-component.
  parentMethod(childInterface: ChildInterface) {
    this.childInterfaces.push(childInterface);
  }

  ngAfterViewChecked() {
    this.elementWidth = this.updateElementWidthRuntime();
    this.ref.detectChanges();
  }
}

子组件

import { Component, AfterViewInit } from '@angular/core';
import { ParentComponent } from '../carousel.component';

@Component({
  selector: 'child-component',
  templateUrl: './carousel-slide.component.html',
  styleUrls: ['./carousel-slide.component.scss'],
})
export class ChildComponent implements AfterViewInit {

  constructor(private parentComponent: ParentComponent) {
  }

  ngAfterViewInit() {
    this.parentComponent.parentMethod(this);
  }
}

应用.html

<parent-component>
    <child-component>
      <div class="box">Content of any height and width</div>
    </child-component>
    <child-component>
      <div class="box">Content of any height and width</div>
    </child-component>
    <child-component>
      <div class="box">Content of any height and width</div>
    </child-component>
</parent-component>

子组件的单元测试

import { async, ComponentFixture, TestBed } from '@angular/core/testing';

import { ParentComponent } from '../parent.component';
import { ChildComponent } from './child.component';

describe('ChildComponent', () => {
  let component: ChildComponent;
  let fixture: ComponentFixture<ChildComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ChildComponent],
      providers: [ParentComponent]
    })
      .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(ChildComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create \'ChildComponent\'', () => {
    expect(component).toBeTruthy();
  });
});

当我尝试在子规范的提供程序中添加 ChangeDetectorRef 时，出现以下错误。

Failed: Encountered undefined provider! Usually this means you have a circular dependencies (might be caused by using 'barrel' index.ts files.)

在谷歌搜索和尝试很多事情后我无法找到解决方案。任何帮助表示赞赏。

Answer 1

您正在使用一个组件作为提供者，这可能不是您的本意。更改您的测试模块以声明您的父组件和子组件。

TestBed.configureTestingModule({
  declarations: [ChildComponent, ParentComponent],
  providers: []  
})