return "backward";
      }
    };
  }

  public void testSerialization_identity() {
    Converter<String, String> identityConverter = Converter.identity();
    SerializableTester.reserializeAndAssert(identityConverter);
  }

  public void testSerialization_reverse() {
    Converter<Long, String> reverseConverter = Longs.stringConverter().reverse();

    return (IdentityConverter<T>) IdentityConverter.INSTANCE;
  }

  /**
   * A converter that always converts or reverses an object to itself. Note that T is now a
   * "pass-through type".
   */
  private static final class IdentityConverter<T> extends Converter<T, T> implements Serializable {
    static final Converter<?, ?> INSTANCE = new IdentityConverter<>();

    @Override