// testing simple creation
    ImmutableSortedSet.Builder<SelfComparableExample> natural = ImmutableSortedSet.naturalOrder();
    assertThat(natural).isNotNull();
    ImmutableSortedSet.Builder<SelfComparableExample> reverse = ImmutableSortedSet.reverseOrder();
    assertThat(reverse).isNotNull();
  }

  private static class SuperComparableExample extends SelfComparableExample {}