assertFalse(iter.hasNext());
    assertThrows(NoSuchElementException.class, () -> iter.next());
  }

  @SuppressWarnings("DoNotCall")
  public void testForEnumerationSingleton() {
    Enumeration<Integer> enumer = enumerate(1);
    Iterator<Integer> iter = Iterators.forEnumeration(enumer);

    assertTrue(iter.hasNext());
    assertTrue(iter.hasNext());