Abstract: A portable test kit for testing electrical and mechanical operation of a locomotive includes one multi-pin connector for connecting to an MU connector on a locomotive. The multi-pin connector is wired in the test kit to a plurality of indicator lights and a plurality of multi-position switches. The lights provide a visual indication of signal presence at the MU connector. The switches enable commands to be placed on the train line through the MU connector to determine if the locomotive is responsive to train line signals. A governor connector and associated indicator lights monitor signals from the locomotive governor system. A plurality of galvanometers are mounted in the kit with corresponding connection jacks for connection to selected points in the locomotive system for simultaneous monitoring of circuit performance. At least a pair of rheostats are connected to the MU connector for controlling loading on selected train line conductors.