public void testAssignController() throws Exception {
   TractionControlRequestMessage msg =
       TractionControlRequestMessage.createAssignController(src, dst);
   byte[] payload = msg.getPayload();
   assertEquals("20 01 00 06 05 05 04 04 03", Utilities.toHexSpaceString(payload));
   assertEquals(src, msg.getSourceNodeID());
   assertEquals(dst, msg.getDestNodeID());
 }