Angular 2：如何在单元测试时模拟 ChangeDetectorRef

typescript
import { ComponentFixture, TestBed } from '@angular/core/testing';
import { Component, ChangeDetectorRef } from '@angular/core';
@Component({
  template: <code>
    <div>{{ value }}</div>
    <button (click)="update()">Update</button>
  </code>
})
class TestComponent {
  value = 'Initial value';
  constructor(private cdr: ChangeDetectorRef) {}
  update() {
    this.value = 'Updated value';
    this.cdr.detectChanges();
  }
}
describe('TestComponent', () => {
  let component: TestComponent;
  let fixture: ComponentFixture<TestComponent>;
  beforeEach(async () => {
    awAIt TestBed.configureTestingModule({
      declarations: [TestComponent]
    }).compileComponents();
  });
  beforeEach(() => {
    fixture = TestBed.createComponent(TestComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });
  it('should update value on button click', () => {
    const button = fixture.nativeElement.querySelector('button');
    button.click();
    fixture.detectChanges();
    const div = fixture.nativeElement.querySelector('div');
    expect(div.textContent).toBe('Updated value');
  });
});