Towards systematic testing of distributed real-time systems

Reproducible and deterministic testing of sequential programs can in most cases be achieved by controlling the sequence of inputs to the program. The behavior of a distributed real-time system, on the other hand not only depends on the inputs but also on the order and timing of the concurrent tasks that execute and communicate with each other and the environment. Hence, sequential test techniques are not directly applicable, since they disregard the significance of order and timing of the tasks. In this paper we present a method for identifying all possible orderings of task starts, preemptions and completions for tasks executing in a distributed real-time system. Together with an accompanying testing strategy, this method allows test methods for sequential programs to be applied, since each identified ordering can be regarded as a sequential program. In the presented analysis and testing strategy, we consider task sets with recurring release patterns, and take into account the effects of clock synchronization and variations in start and execution times of the involved tasks