public void testOf_subSetSerialization() {
    SortedSet<String> set = of("e", "f", "b", "d", "c");
    SerializableTester.reserializeAndAssert(set.subSet("c", "e"));
  }

  public void testOf_first() {
    SortedSet<String> set = of("e", "f", "b", "d", "c");
    assertEquals("b", set.first());
  }

  public void testOf_last() {
    SortedSet<String> set = of("e", "f", "b", "d", "c");