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

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testOf_serialization() {
    SortedSet<String> set = of("e", "f", "b", "d", "c");
    SortedSet<String> copy = SerializableTester.reserializeAndAssert(set);
    assertTrue(elementsEqual(set, copy));

            Predicates.in(differentOrder))
        .addEqualityGroup(Predicates.in(differentNums))
        .testEquals();
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testIn_serialization() {
    checkSerialization(Predicates.in(Arrays.asList(1, 2, 3, null)));
  }

  public void testIn_handlesNullPointerException() {
    class CollectionThatThrowsNPE<T> extends ArrayList<T> {