
  const fieldset = menulist.appendChild(document.createElement('fieldset'));
  fieldset.setAttribute("checkable", "single");
  const single1 = fieldset.appendChild(document.createElement('menuitem'));

  single1.checked = true;
  assert_true(single1.checked, true);
  fieldset.removeAttribute('checkable');
  assert_false(single1.checked, false,
      "menuitem gets unchecked after fieldset becomes uncheckable");
  single1.checked = true;
  assert_false(single1.checked,
      "menuitem cannot become checked 