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");
    assertEquals(set, Sets.newTreeSet(asList("a", "b", "c")));
    assertEquals(Sets.newTreeSet(asList("a", "b", "c")), set);