在Angular 2中使用SimpleChanges测试ngOnChanges

import { Component, Input, OnChanges, SimpleChanges } from '@angular/core';

@Component({
  selector: 'app-example',
  template: `
    <h1>{{ title }}</h1>
  `
})
export class ExampleComponent implements OnChanges {
  @Input() title: string;

  ngOnChanges(changes: SimpleChanges) {
    if (changes.title) {
      console.log('Title changed:', changes.title.currentValue);
    }
  }
}

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { ExampleComponent } from './example.component';

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

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      declarations: [ ExampleComponent ]
    })
    .compileComponents();
  });

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

  it('should call ngOnChanges when title changes', () => {
    spyOn(component, 'ngOnChanges');
    component.title = 'New Title';
    fixture.detectChanges();
    expect(component.ngOnChanges).toHaveBeenCalled();
  });
});