1. 确认在测试文件中引入了需要的依赖：import { ScrollingModule } from '@angular/cdk/scrolling';
2. 使用 fakeAsync 和 tick 解决异步问题：

import { ComponentFixture, fakeAsync, TestBed, tick } from '@angular/core/testing'; import { ScrollingModule } from '@angular/cdk/scrolling';

...

it('should render 5 items', fakeAsync(() => { const fixture: ComponentFixture = TestBed.createComponent(TestComponent); fixture.detectChanges();

// simulate an initial scroll event to trigger CDK's onContentScrolled const scrollContent: HTMLElement = fixture.nativeElement.querySelector('.cdk-virtual-scroll-content-wrapper'); scrollContent.scrollTop = 10; scrollContent.dispatchEvent(new Event('scroll')); tick();

fixture.detectChanges();

const items: NodeListOf = fixture.nativeElement.querySelectorAll('li'); expect(items.length).toEqual(5); // assert that there are 5 items visible }));