Angular Jasmine TypeError: Cannot read property 'scroll' of null

Question

I am getting below error while running jasmine unit test in angular

Error:

TypeError: Cannot read property 'scroll' of null at at BoxComponent.ngAfterViewInit (http://localhost:9876/_karma_webpack_/src/app/components/box/box.component.ts:289:14)

// component 

ngAfterViewInit() {
    document.querySelector('.form-div .form-box').scroll(0, 0);
  }
  
//unit test

it('should call ngAfterViewInit', () => {
    component.ngAfterViewInit();
    spyOn(document.querySelector('.form-div .form-box'), 'scroll').withArgs(0, 0).and.callThrough();
    expect(document.querySelector('.form-div .form-box').scroll).toHaveBeenCalledWith(0, 0);
    expect(component.ngAfterViewInit).toBeTruthy();
  });
  
  
// Error

TypeError: Cannot read property 'scroll' of null
    at <Jasmine>
    at BoxComponent.ngAfterViewInit (http://localhost:9876/_karma_webpack_/src/app/components/box/box.component.ts:289:14)

Anamika Dadhich · Accepted Answer · 2020-05-28 12:30:31Z

0

You are supposed to use $document instead of document then you can mock it in your tests. you can refer : Angular js unit test mock document

answered May 28, 2020 at 12:30

Anamika Dadhich

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1 Comment

user13111402 Over a year ago

I am working on Angular 9. $document i guess is used in angularjs. please correct me if i am wrong

user13111402 · Accepted Answer · 2020-05-28 14:23:46Z

0

I tried below code and it worked

el: ElementRef

 ngAfterViewInit() {
    if (this.el && this.el.nativeElement && this.el.nativeElement.parentElement) {
      this.el.nativeElement.parentElement.scrollTop = 0;
    }
  }

answered May 28, 2020 at 14:23

user13111402

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