List<String> expected = emptyList();
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
  }

  public void testFilterMatchAll() {
    Iterator<String> unfiltered = Lists.newArrayList("foo", "bar").iterator();
    Iterator<String> filtered = filter(unfiltered, Predicates.alwaysTrue());
    List<String> expected = Lists.newArrayList("foo", "bar");