Testing Angular 2/4 directive with mouse wheel events

I have a directive that prevents scrolling of the parent container, but I got stuck on testing it. How to test this mouse events and the entire directive? Can anyone help me please?

import { Directive, ElementRef, OnInit, OnDestroy, Input, NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

    @Directive({
      selector: '[preventParentScroll]'
    })
    export class PreventScrollDirective implements OnInit, OnDestroy {
      private mouseWheelEventHandler = (event: any) => this.onMouseWheel(event);
      constructor(private element: ElementRef) {
      }

      ngOnInit() {
        const element: Element = this.element.nativeElement;
        element.addEventListener('mousewheel', this.mouseWheelEventHandler);
        element.addEventListener('DOMMouseScroll', this.mouseWheelEventHandler);
      }

      ngOnDestroy() {
        const element: Element = this.element.nativeElement;
        element.removeEventListener('mousewheel', this.mouseWheelEventHandler);
        element.removeEventListener('DOMMouseScroll', this.mouseWheelEventHandler);
      }

      onMouseWheel(event: any) {
        const element: any = this.element.nativeElement;
        const { scrollTop, scrollHeight, clientHeight } = element;
        const delta = (event.type === 'DOMMouseScroll' ? event.detail * -40 : event.wheelDelta);
        const up = delta > 0;

        const prevent = () => {
          event.stopPropagation();
          event.preventDefault();
          event.returnValue = false;
          return false;
        };

        if (!up && -delta > scrollHeight - clientHeight - scrollTop) {
          element.scrollTop = scrollHeight;
          return prevent();
        } else if (up && delta > scrollTop) {
          element.scrollTop = 0;
          return prevent();
        }
      }
    }