Optional<String> z = Optional.of("z");

    Comparator<Optional<String>> comparator = emptiesLast(comparing(String::length));
    testComparator(comparator, z, abc, empty);

    // Just demonstrate that no explicit type parameter is required
    Comparator<Optional<String>> unused = emptiesLast(naturalOrder());
  }

  public void testMinMaxNatural() {
    assertThat(min(1, 2)).isEqualTo(1);