@Override
    public TransformationOutput transform(Message message) {
      String blobIdStr = message.getMessageInfo().getStoreKey().getID();
      if (errorKeys.contains(blobIdStr)) {
        return new TransformationOutput(new MessageFormatException("CRC error", MessageFormatErrorCodes.DataCorrupt));
      }
      return new TransformationOutput(message);
    }
A transformer that throws errors when transforming a given set of keys
ambry-replication/src/test/java/com/github/ambry/replication/ReplicationTestHelper.java