How to use the @ember/test-helpers.focus function in @ember/test-helpers

test('it renders', async function(assert) {
  this.render(hbs`{{foo-bar}}`);

  await focus('.foo');
  assert.ok(true);
});

test('visiting /foo', async function(assert) {
  await visit('/foo');

  await focus('input');
  await blur('input');
  await triggerEvent('#bar', 'mouseenter');
  assert.equal(currentURL(), '/foo');
});

test('DOM interactions', async () => {
    await render(hbs`<div class="message">Hello, world</div>`);

    await click('.message');
    await doubleClick('.message');
    await tap('.message');
    await focus('.message');
    await blur('.message');
    await triggerEvent('.message', 'custom-event');
    await triggerKeyEvent('.message', 'keydown', 'Enter', { ctrlKey: true });
    await fillIn('.message', 'content');

    const messageElement = find('.message')!;
    await click(messageElement);
    await doubleClick(messageElement);
    await tap(messageElement);
    await focus(messageElement);
    await blur(messageElement);
    await triggerEvent(messageElement, 'custom-event');
    await triggerKeyEvent(messageElement, 'keydown', 'Enter', { ctrlKey: true });
    await fillIn(messageElement, 'content');
    await typeIn(messageElement, 'content');

test('and again', async function(assert) {
  this.render(hbs`{{foo-bar}}`);

  await tap('foo');
  let el = findWithAssert('.foo input');

  await fillIn(el, value);
  await triggerEvent('.foo input', 'change');
  await triggerKeyEvent('bar', 'keypress', 13, modifiers);

  await focus('.foo input');
  await blur('.foo input');

  assert.ok(findAll('.baz')[1].classList.contains('selected'));
});

await render(hbs`<div class="message">Hello, world</div>`);

    await click('.message');
    await doubleClick('.message');
    await tap('.message');
    await focus('.message');
    await blur('.message');
    await triggerEvent('.message', 'custom-event');
    await triggerKeyEvent('.message', 'keydown', 'Enter', { ctrlKey: true });
    await fillIn('.message', 'content');

    const messageElement = find('.message')!;
    await click(messageElement);
    await doubleClick(messageElement);
    await tap(messageElement);
    await focus(messageElement);
    await blur(messageElement);
    await triggerEvent(messageElement, 'custom-event');
    await triggerKeyEvent(messageElement, 'keydown', 'Enter', { ctrlKey: true });
    await fillIn(messageElement, 'content');
    await typeIn(messageElement, 'content');

    const allMessages = findAll('.message');
    for (const element of allMessages) {
        await click(element);
    }

    const root = getRootElement();
    await click(root);
});