assert.expect & testing async code

components.my-component\.js

import Component from '@glimmer/component';

export default class extends Component {

}

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

<button
  {{on "mousedown" @onMouseDown}}
  {{on "mouseup" @onMouseUp}}
>
  Click me
</button>

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

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

module('assert.expect vs verifySteps use case', function(hooks) {
  setupRenderingTest(hooks);

  test('wrong', async function(assert) {
    
    // Test incorrectly passes.
    // Due to not using assert.expect
    
    this.handleMouseDown = () => assert.ok(true, 'fires mouse down action');
    this.handleMouseUp = () => assert.ok(true, 'fires mouse up action');
    
    await render(hbs`
      <MyComponent
        @onMouseDown={{this.handleMouseDown}}
        @onMouseUp={{this.handleMouseUp}}
       />
    `);
    
    await triggerEvent('button', 'mousedown');
    // await triggerEvent('button', 'mouseup');
  });
  
  test('better', async function(assert) {
    
    // Better, test fails due to use of assert.expect
    
    assert.expect(2);
    
    this.handleMouseDown = () => assert.ok(true, 'fires mouse down action');
    this.handleMouseUp = () => assert.ok(true, 'fires mouse up action');
    
     await render(hbs`
      <MyComponent
        @onMouseDown={{this.handleMouseDown}}
        @onMouseUp={{this.handleMouseUp}}
       />
    `);
    
    await triggerEvent('button', 'mousedown');
    // await triggerEvent('button', 'mouseup');
  });
  
  test('best', async function(assert) {
    
    // Best, use correct tool for the job...
    
    this.handleMouseDown = () => assert.step('fires mouse down action');
    this.handleMouseUp = () => assert.step('fires mouse up action');
   
    await render(hbs`
      <MyComponent
        @onMouseDown={{this.handleMouseDown}}
        @onMouseUp={{this.handleMouseUp}}
       />
    `);

    await triggerEvent('button', 'mousedown');
    // await triggerEvent('button', 'mouseup');
    
    assert.verifySteps(['fires mouse down action', 'fires mouse up action'])
  });
});

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"
  }
}