如何在Angular 8的ngIf语句中测试子组件的外观

<app-child *ngIf="condition"></app-child>

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

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

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

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

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

  // Add more test cases here
});

it('should show child component when condition is true', () => {
  component.condition = true;
  fixture.detectChanges();
  const childComponent = fixture.debugElement.query(By.directive(ChildComponent));
  expect(childComponent).toBeTruthy();
});

it('should hide child component when condition is false', () => {
  component.condition = false;
  fixture.detectChanges();
  const childComponent = fixture.debugElement.query(By.directive(ChildComponent));
  expect(childComponent).toBeFalsy();
});