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);
    assertThat(min(2, 1)).isEqualTo(1);
    assertThat(max(1, 2)).isEqualTo(2);
    assertThat(max(2, 1)).isEqualTo(2);
  }