private void sendSerialMessageToAll() {
    if (getCache() instanceof GemFireCacheImpl) {
      try {
        org.apache.geode.distributed.internal.SerialAckedMessage msg =
            new org.apache.geode.distributed.internal.SerialAckedMessage();
        msg.send(getCache().getDistributionManager().getNormalDistributionManagerIds(), false);
      } catch (Exception e) {
        throw new RuntimeException("Unable to send serial message due to exception", e);
      }
    }
  }
returns a map of keys->versiontags for the test region
geode-dunit/src/main/java/org/apache/geode/cache30/MultiVMRegionTestCase.java