public void test_immutable() {

    Class<ZonedDateTime> cls = ZonedDateTime.class;
    assertTrue(Modifier.isPublic(cls.getModifiers()));
    assertTrue(Modifier.isFinal(cls.getModifiers()));
    Field[] fields = cls.getDeclaredFields();
    for (Field field : fields) {
      if (field.getName().contains("$") == false) {
        assertTrue(Modifier.isPrivate(field.getModifiers()));
        assertTrue(Modifier.isFinal(field.getModifiers()));
      }
    }
  }

  // -----------------------------------------------------------------------
  @Test(groups = { "tck" }