如何在此 Jest 测试中触发 window 加载事件？

Question

I'm trying to set up my first DOM-manipulation/JQuery Jest test in my Rails project. In its essential form at the moment, I'm just trying to clear a basic hurdle of 'imported Javascript functions do anything at all'.

To that end, I have the following code in PledgeFormUpdates.js.test:

'use strict';

import pledge_form_updates from '../../app/javascript/components/PledgeFormUpdates.js';

test('Displays GDPR checkbox on EU country selection', () => {

  // Set up our document body
  document.body.innerHTML =
    '<select id="pledge_pledgor_home_country" class="country-select"></select>'// +

    pledge_form_updates();
    const $ = require('jquery');

    $(window).trigger('load');
    $("#pledge_pledgor_home_country").trigger('change');
});

And in PledgeFormUpdates.js I have the following:

export default function() {
  console.log('hello world');
  window.addEventListener("load", function() {

    console.log('mellow curled');
    $("#pledge_pledgor_home_country").change(function() {
      console.log('yellow twirled')
    });
  });
};

So when I run the test, I'm expecting to see printout including 'hello world', 'mellow curled' and 'yellow twirled'. But in practice it's stopping after the first output, and so presumably the window load event isn't actually getting triggered (which I confirmed by commenting out the window.addEventListener... line, then seeing all three printouts).

What am I doing wrong here - or rather, how should I trigger the load event? (I also tried $(window).load(); , but that just raises a TypeError)

Answer 1

I found a workaround for this, though it seems quite hacky. In the tested file, if I substitute the line

window.addEventListener("load", function() { ,

with

$(window).on("load", function() {

then running the test (including the $(window).trigger('load'); statement) prints all of the log lines.

I must be missing something, because I can't believe that Jest would require JQuery to trigger a page load event, but for now at least this works.