要在HostListener函数的条件Else部分运行单元测试，我们可以使用TestBed和ComponentFixture。首先，创建一个测试宿主组件，并在其中定义一个mock函数来测试条件Else部分。然后，使用TestBed创建组件实例，并使用ComponentFixture.detectChanges()触发变更检测周期。最后，使用spyOn()方法监听mock函数的调用。以下是示例代码：

组件：

import { Component, HostListener } from '@angular/core';

@Component({
  selector: 'my-cmp',
  template: `
Component
`
})
export class MyComponent {
  @HostListener('window:resize', ['$event'])
  onResize(event) {
    if (event.target.innerWidth > 768) {
      console.log('Larger than 768px');
    } else {
      this.onSmallerScreen();
    }
  }

  onSmallerScreen() {
    console.log('Smaller than 768px');
  }
}

测试：

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

describe('MyComponent', () => {
  let component: MyComponent;
  let fixture: ComponentFixture;
  let onSmallerScreenSpy: jasmine.Spy;

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

  beforeEach(() => {
    fixture = TestBed.createComponent(MyComponent);
    component = fixture.componentInstance;
    onSmallerScreenSpy = spyOn(component, 'onSmallerScreen');
    fixture.detectChanges();
  });

  it('should call onSmallerScreen when window width is smaller than 768px', () => {
    const event = new Event('resize');
    Object.defineProperty(event.target, 'innerWidth', { writable: true, configurable: true, value: 500 });
    window.dispatchEvent(event);
    expect(onSmallerScreenSpy).toHaveBeenCalled();
  });

  it('should call console.log when window width is larger than 768px', () => {
    const event = new Event('resize');
    Object.defineProperty(event.target, 'innerWidth', { writable: true, configurable: true, value: 800 });
    window.dispatchEvent(event);