Angular: How I can test @HostListener in jasmine?

Question

I have the next code in angular's component:

@HostListener('window:scroll', []) onWindowScroll() {
  this.showScrollToTop = false;
}

How can I test this in jasmine? How to to initiate window scroll event?

Answer 1

Testing for window:scroll:

it('should do something on window scroll', () => {
  window.dispatchEvent(new Event('scroll'));
  expect(...)....
});

Answer 2

You can try to make simple JS scroll by calling scrollTo function on window.

In case you want to make scroll top it will be:

window.scrollTo(0, 0);

Update

var scrollEvent = document.createEvent('CustomEvent');
scrollEvent.initCustomEvent( 'scroll', false, false, null );

window.dispatchEvent(scrollEvent)