S(element, comment) {
  assert_false(element.matches(':valid'), comment ? (comment + ' - :valid') : undefined);
  assert_true(element.matches(':invalid'), comment ? (comment + ' - :invalid') : undefined);
}

test(() => {
  const container = document.getElementById('container');
  container.innerHTML = '<form><fieldset><my-control>';
  const form = container.querySelector('form');
  const fieldset = container.querySelector('fieldset');
  const control = container.querySelector('my-control');

  isValidAccord