DataInputStream in = new DataInputStream(new ByteArrayInputStream(out.toByteArray()));
Command header = pduReader.readPDUHeader(in);
assertEquals(header.getCommandId(), SMPPConstant.CID_GENERIC_NACK, "Unexpected command_id");
byte[] pdu = pduReader.readPDU(in, header);
GenericNack nack = decomposer.genericNack(pdu);
assertNotNull(nack);
}