DEV Community

Cover image for Unit test CHILD component from PARENT component's test case
MD ASHRAF
MD ASHRAF

Posted on

Unit test CHILD component from PARENT component's test case

#angular #unittest #learning #typescript

Here are some ways to get a child component in a parent test case in Angular:

  1. Using fixture.debugElement.query(): 
const childDebugElement = fixture.debugElement.query(By.directive(ChildComponent));
const childComponent = childDebugElement.componentInstance;
Enter fullscreen mode Exit fullscreen mode

This method uses the debugElement property of the fixture to query for the child component.

2.Using fixture.debugElement.queryAll():

const childDebugElements = fixture.debugElement.queryAll(By.directive(ChildComponent));
const childComponents = childDebugElements.map(de => de.componentInstance);
Enter fullscreen mode Exit fullscreen mode

This method uses the queryAll method to retrieve an array of debug elements that match the child component directive.

3.Using fixture.nativeElement.querySelector():

const childElement = fixture.nativeElement.querySelector('app-child');
const childComponent = fixture.debugElement.query(By.css('app-child')).componentInstance;
Enter fullscreen mode Exit fullscreen mode

This method uses the nativeElement property of the fixture to query for the child component element, and then uses the debugElement property to retrieve the component instance.

4.Using a test double or spy:

const childComponentSpy = jasmine.createSpyObj('ChildComponent', ['methodName']);
TestBed.configureTestingModule({
  declarations: [ParentComponent],
  providers: [{ provide: ChildComponent, useValue: childComponentSpy }]
});
Enter fullscreen mode Exit fullscreen mode

This method creates a test double or spy for the child component, allowing you to test the parent component's interactions with the child component without actually rendering the child component.

5.Using ViewChild:
// parent.component.ts

@ViewChild(ChildComponent) childComponent: ChildComponent;
Enter fullscreen mode Exit fullscreen mode

// parent.component.spec.ts

const childComponent = fixture.componentInstance.childComponent;
Enter fullscreen mode Exit fullscreen mode

This method uses the ViewChild decorator to retrieve a reference to the child component instance in the parent component.

These are just a few examples of how you can get a child component in a parent test case in Angular. The best approach will depend on your specific testing needs and requirements.

Top comments (0)