InputStream inputStream = session.getInputStream();
PacketListener listener = Whitebox.getInternalState(inputStream, PacketListener.class);
// build invalid packet with out of order sequence
String base64Data = StringUtils.encodeBase64("Data");
DataPacketExtension dpe = new DataPacketExtension(sessionID, 123, base64Data);
Message dataMessage = new Message();
dataMessage.addExtension(dpe);
// add data packets
listener.processPacket(dataMessage);