r single3 checked]");
  assert_true(single3.checked, "single3 IS checked [after single3 checked]");
  assert_true(single3.matches(":checked"),
      "single3 IS :checked [after single3 checked]");
}, "checkable menuitem exclusivity");

test(() => {
  assert_false(multiple1.checked, "multiple1 not checked");
  assert_false(multiple1.matches(":checked"), "multiple1 not :checked");
  assert_false(multiple2.checked, "multiple2 not checked");
  assert_false(multiple2.matches(":checked"), "multiple2 not :checked"