private void checkEvent(TransactionEvent event) {
      List<CacheEvent<?, ?>> events = event.getEvents();
      System.out.println("MyTestTransactionListener.checkEvent: events are " + events);
      for (CacheEvent<?, ?> cacheEvent : events) {
        if (((LocalRegion) cacheEvent.getRegion()).isPdxTypesRegion()) {
          throw new UnsupportedOperationException("found internal event: " + cacheEvent + " region="
              + cacheEvent.getRegion().getName());
        }
      }
    }
add a listener and writer that will throw an exception when invoked if events are for internal
regions
geode-core/src/distributedTest/java/org/apache/geode/pdx/PdxSerializableDUnitTest.java