Ember Test Helpers

gistfile1.js

```js
// x-img-test.js
import { module, test } from 'qunit';
import { setupRenderingTest } from 'ember-qunit';
import { render } from '@ember/test-helpers';
import hbs from 'htmlbars-inline-precompile';

module('Integration | Component | x-img', function(hooks) {
  setupRenderingTest(hooks);

  test('it renders', async function(assert) {
    await render(hbs`{{x-img}}`);

    let img = this.element.querySelector('img');

    // Next assertion will fail without either the following line,
    // or a test waiter registered in the component:
    // await waitUntil(() => img.complete);

    assert.ok(img.complete, 'image has loaded');
  });
});
```

```hbs
<img src={{src}}>
```
    
```js
// components/x-img.js
import Component from '@ember/component';
import Ember from 'ember';
import { registerWaiter, unregisterWaiter } from '@ember/test';

export default Component.extend({
  didInsertElement() {
    this._super(...arguments);
    if (Ember.testing) {
      this._isComplete = () => this.element.querySelector('img').complete;
      registerWaiter(this._isComplete);
    }
  },

  willDestroyElement() {
    if (Ember.testing) {
      unregisterWaiter(this._isComplete);
    }

    this._super(...arguments);
  },

  src: "https://emberjs.com/images/tomsters/original-72df3a45.png"
});
```