Mutation Testing of Simulink Cyber-Physical System Models: Challenges and Solutions in Practice
Several experience reports illustrate that mutation testing is capable of supporting a shift-left testing strategy, especially in industries where late bug discovery incurs very high costs and risks. In the context of cyber-physical systems, a shift left implies that engineers need to test the design models used to simulate, prototype, and analyse the feasibility of the system under design. In this paper, we analyse the challenges we encountered and the lessons we learned when incorporating mutation testing in the context of DUCO, a company producing ventilation systems for buildings. The engineers within DUCO have years of experience with model-based engineering centered around Simulink and StateFlow, including unit tests for their models. During a pilot project with our tool prototype MUT4SLX we learned that equivalent mutants, requirement traceability, and mutation testing for Stateflow represent particular challenges not yet reported in the academic literature.