Combining STPA With CoFI to Generate Requirements and Test Cases for Safety-Critical System

For the development of safety-critical systems, it is claimed that system-theoretic process analysis (STPA) identifies more software loss scenarios and component interaction loss scenarios when compared to failure modes and effects analysis. A challenge related to the development of these systems is to perform system safety verification. We claim that there is a lack of systematic approaches that allow test cases generation for verification (testing) of the system safety requirements. Conformance and fault injection (CoFI) is a systematic model-based approach to create software system test cases of critical systems, using finite state machines. We investigate how to combine STPA with CoFI so that requirements are identified and test cases are generated concomitantly. We describe the steps of the approach using it for the insulin pump with a smartphone system. The approach has been shown to be systematic and capable of generating test cases for the STPA identified requirements.