.addEqualityGroup(alwaysFalse)
        .addEqualityGroup(Functions.identity())
        .testEquals();
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testForPredicateSerializable() {
    checkCanReserialize(Functions.forPredicate(Predicates.equalTo(5)));
  }

  public void testConstant() {
    Function<@Nullable Object, Object> f = Functions.<Object>constant("correct");