mouseleave test helper

components.my-component\.js

import Component from '@glimmer/component';
import { tracked} from '@glimmer/tracking';
import { action } from '@ember/object';

export default class MyComponentComponent extends Component {
  @tracked mouseLeave = false;
  @tracked mouseLeaveChild = false;

  @action
  handleLeave() {
    this.mouseLeave = true
  }

  @action
  handleLeaveChild() {
    this.mouseLeaveChild = true
  }
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

templates.components.my-component\.hbs

<div class="my-component" data-mouse-leave="{{this.mouseLeave}}" {{on "mouseleave" this.handleLeave}}>

  <button type="button" class="my-component__child" data-mouse-leave="{{this.mouseLeaveChild}}" {{on "mouseleave" this.handleLeaveChild}}>
  </button>
</div>

tests.integration.components.my-component-test\.js

import { module, test } from 'qunit';
import { setupRenderingTest } from 'ember-qunit';
import { render, find, triggerEvent } from '@ember/test-helpers';
import hbs from 'htmlbars-inline-precompile';

module('TODO: put something here', function(hooks) {
  setupRenderingTest(hooks);

  test('it renders', async function(assert) {
    await render(hbs`<MyComponent />`);

    await triggerEvent('.my-component__child', 'mouseleave');

    assert.equal(
      find('.my-component').getAttribute('data-mouse-leave'),
      'false',
      'mouse did not leave the parent'
    );
    
    assert.equal(
      find('.my-component__child').getAttribute('data-mouse-leave'),
      'true',
      'mouse left the child'
    );
  });
});

tests.test-helper\.js

import Application from '../app';
import config from '../config/environment';
import { setApplication } from '@ember/test-helpers';
import { assign } from '@ember/polyfills';
import { start } from 'ember-qunit';

let attributes = {
  rootElement: '#test-root',
  autoboot: false
};
attributes = assign(attributes, config.APP);

let application = Application.create(attributes);
setApplication(application);

start();

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": true
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}