assertThrows(UnsupportedOperationException.class, () -> iterator.set("a"));
    assertThrows(UnsupportedOperationException.class, () -> iterator.add("a"));
  }

  public void testEmptyModifiableIterator() {
    Iterator<String> iterator = Iterators.emptyModifiableIterator();
    assertFalse(iterator.hasNext());
    assertThrows(NoSuchElementException.class, () -> iterator.next());