Testing if an event has been triggered in Jasmine

Question

How do you test if an event has been fired in Jasmine without jquery-jasmine ?

I'm working on a project where we don't use jQuery (wohoo), and I'm trying to write a unit test for my menu triggering function. It works like this:

• You click a button
• My testable component then runs document.dispatchEvent(new CustomEvent('menu.toggle'))
• I want to test that the component indeed dispatched the custom event.

How do I test this?

Answer 1

Played around a bit and found a solution that worked well:

import triggerEvent from 'trigger-event';
import component from './components/site-menu';

describe('triggering menu button', () => {
  let menuToggleSpy;
  beforeEach(() => {
    menuToggleSpy = jasmine.createSpy('event');
    component();
  });

  it('dispatches menu.toggle event', () => {
    document.addEventListener('menu.toggle', menuToggleSpy);

    const $trigger = document.querySelector('.js-trigger-main-menu');
    triggerEvent($trigger, 'click');

    expect(menuToggleSpy).toHaveBeenCalled();
  });
});

Basically create a new spy called 'event', adding it as a event handler for my event, and then verifying it's been called.

If there are better ways to do this, I'll be more than happy to accept a different answer.