Applying Combinatorial Testing to High-Speed Railway Track Circuit Receiver

A track circuit is a critical component of a modern railway system. The circuit is used to detect the absence of a train on rail tracks and produce corresponding control signals. A railway track has many block sections, each of which has a separate track circuit device. A track circuit receiver analyzes signals sent from a track circuit sender and produces a signal to control a relay. When the train is in a section, the relay must be down, otherwise, the relay must be up. We tested a track circuit receiver product that is widely used in high-speed railways in China. We extracted three input parameters from a signal sent to the receiver and create an Input Domain Model (IDM). We generated pair-wise test sets using the IDM. Moreover, from the requirements, we derived two UML finite state machines (FSMs) in the presence of multiple signals. In the FSMs, a transition can represent a signal input to the system. We first generated test paths from the FSMs, and then applied combinatorial testing to the parameters used in the test paths. We generated a total of 13,971 tests, which allowed us to detect four new faults in a release version of the product.