Testing embedded real-time systems

An embedded real-time system consists of a number of components (processes) that run concurrently and communicate with each other under predefined timing constraints. The correctness of such systems is important, since they are used in an increasingly number of safety-critical systems. To improve the quality of these systems, two techniques can be used, namely verification of the specification and testing of the implementation. In this paper, we consider the testing of embedded real-time components. In our model, the system is modeled as a set of communicating timed input-output automata (CTIOA). One CTIOA specifies the component to be tested and the remaining CTIOAs represent the context. The relationship between the component to be tested and the other ones should be taken into account for test case generation. We discuss how testing in context differs from testing in isolation. We review the fault model in the context of CTIOA and we propose an approach for test case generation from an embedded CTIOA. This approach consists of three steps. First, we avoid the composition of all machines by selecting, based on a specific criterion, only some parts of the CTIOA's context that affect (or are affected by) the specification. Then we determine the partial product of the specification and the selected parts of the context. Finally, we apply the timed Wp-method (A. En-Nouaary et al., 1998) to the resulting timed input-output automata. The quality of the resulting partial product is strongly dependent on the criterion used to select the parts of the context to consider in test case generation.