@Test
  public void testSerializable() throws Exception {
    // TODO: when we use @BeforeClass, we can pay the cost of class path scanning only once.
    for (Class<?> classToTest :
        findClassesToTest(loadClassesInPackage(), SERIALIZABLE_TEST_METHOD_NAMES)) {
      if (Serializable.class.isAssignableFrom(classToTest)) {
        try {
          Object instance = tester.instantiate(classToTest);
          if (instance != null) {