custom-elements/form-associated/form-reset-callback.html

<!DOCTYPE html>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
class MyControl extends HTMLElement {
  static get formAssociated() { return true; }

  constructor() {
    super();
    this.resetCalled_ = false;
  }

  formResetCallback() {
    this.resetCalled_ = true;
  }
  get resetCalled() { return this.resetCalled_; }
}
customElements.define('my-control', MyControl);

test(() => {
  document.body.insertAdjacentHTML('beforeend',
      '<form><my-control></my-control></form>');
  let form = document.body.lastChild;
  let custom = form.firstChild;
  form.reset();
  assert_true(custom.resetCalled);
}, 'form.reset() should trigger formResetCallback');

test(() => {
  document.body.insertAdjacentHTML('beforeend',
      '<form><my-control></my-control><output>default</output></form>');
  let form = document.body.lastChild;
  let custom = form.firstChild;
  let output = form.lastChild;
  output.value = 'updated';
  output.addEventListener('DOMSubtreeModified', () => {
    assert_false(custom.resetCalled, 'formResetCallback should not be ' +
                 'called before built-in control\'s reset');
  });
  form.reset();
  assert_true(custom.resetCalled);
}, 'form.reset(): formResetCallback is called after reset of the last ' +
   'built-in form control and before the next statement.');

promise_test(() => {
  document.body.insertAdjacentHTML('beforeend',
      '<form><my-control></my-control><input type=reset></form>');
  let form = document.body.lastChild;
  let custom = form.firstChild;
  let resetButton = form.lastChild;
  assert_false(custom.resetCalled);
  resetButton.click();
  assert_false(custom.resetCalled);
  return Promise.resolve().then(() => assert_true(custom.resetCalled));
}, 'Clicking a reset button invokes formResetCallback in a microtask');
</script>
</body>