A method is described for testing a train control system configured to control at least two locomotives. The train control system includes a control unit on each locomotive and is configured to control the locomotives using communication links between the control units. The method includes establishing communication between a testing device and a first locomotive control unit, and emulating a second locomotive control unit using the testing device. The testing method allows control system testing to be performed using a hand-held testing device in place of a second locomotive and facilitates testing of repeaters.