A trainline integrity locomotive test device is provided that is configured to provide conventionally provided End-Of-Train (EOT) functionality required for a single locomotive test as well as functionality necessary for troubleshooting electrical problems in trainline electrical conductors, wherein the trainline integrity locomotive test device includes a reduced number of components in comparison with a conventional EOT device. Additionally, the test device is provided in more compact, durable and robust form relative to conventional EOT devices. As part of the transmission of trainline integrity data from the test device to the Head-End-Unit, a communications heartbeat signal is substituted for brake pipe pressure conventionally detected by EOT devices, so as to provide an indication of data communication reliability.