Error if the target element is not a form-associated custom element");

test(() => {
  const control = document.createElement('my-control');
  let invalidCount = 0;
  control.addEventListener('invalid', e => {
    assert_equals(e.target, control);
    assert_true(e.cancelable);
    ++invalidCount;
  });

  assert_true(control.i.checkValidity(), 'default state');
  assert_equals(invalidCount, 0);

  control.i.setValidity({customError:true}, 'foo');
  assert_false(control.i.checkValidity());
  assert_equals(i