Angular: How I can test @HostListener in jasmine?

Testing for window:scroll:

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

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)