    "menuitem direct child of menulist is not checked");
  assert_false(nonCheckable.matches(":checked"));
  nonCheckable.checked = true;
  assert_equals(nonCheckable.checked, false,
      "menuitem direct child of menulist cannot be checked");
  assert_false(nonCheckable.matches(":checked"));

  const checkable = document.querySelector("#menulist-menuitem-checkable");
  assert_equals(nonCheckable.checked, false,
      "checkable menuitem is not checked");
  assert_false(nonCheckable.matches(":checked"));
 