ImmutableSortedSet.Builder<String> zat =
        ImmutableSortedSet.<String>orderedBy(STRING_LENGTH).add("a", "bb", "dddd", "ccc");
    ImmutableSortedSet<String> sortedSet = zis.combine(zat).build();
    assertThat(sortedSet).containsExactly("a", "bb", "ccc", "dddd").inOrder();
  }

  public void testEquals_bothDefaultOrdering() {
    SortedSet<String> set = of("a", "b", "c");