Testing of multi-tasking real-time systems with critical sections

In this paper we address the problem of testing real-time software in the functional domain. In order to achieve reproducible and deterministic test results of an entire multitasking real-time system it is essential not to only consider inputs and outputs, but also the order in which tasks communicate and synchronize with each other. We present a deterministic white-box system-level control-flow testing method for deterministic integration testing of real-time system software. We specifically address fixed priority scheduled real-time systems where synchronization is resolved using the Priority Ceiling Emulation Protocol or offsets in time. The method includes a testing strategy where the coverage criterion is defined by the number of paths in the system control flow. The method also includes a reachability algorithm for deriving all possible paths in terms of orderings of task starts, preemptions and completions of tasks executing in a real-time system. The deterministic testing strategy allows test methods for sequential programs to be applied, since each identified ordering can be regarded as a sequential program.