Traffic-aware Stress Testing of Distributed Real-Time Systems Based on UML Models in the Presence of Time Uncertainty

In a previous work, we reported and experimented with a stress testing methodology to detect network traffic- related real-time (RT) faults in distributed real-time systems (DRTSs) based on the design UML models. The stress methodology, referred to as time-shifting stress test methodology (TSSTM), aimed at increasing chances of discovering RT faults originating from network traffic overloads in DRTSs. The TSSTM uses the UML 2.0 model of a system under test (SUT), augmented with timing information, and is based on an analysis of the control flow in UML sequence diagrams. In order to devise deterministic test requirements (from time point of view) that yield the maximum stress test scenario in terms of network traffic in a SUT, the TSSTM methodology requires that the timing information of messages in sequence diagrams is available and as precise as possible. In reality, however, the timing information of messages is not always available and precise. As we demonstrate using a case study in this work, the effectiveness of the stress test cases generated by TSSTM is very sensitive to such time uncertainty. In other words, TSSTM might generate imprecise and not necessarily maximum stressing test cases in the presence of such time uncertainty and, thus, it might not be very effective in revealing RT faults. To address the above limitation of TSSTM, we present in this article a modified testing methodology which can be used to stress test systems when the timing information of messages is imprecise or unpredictable. The stress test results of applying the new test methodology to a prototype DRTS indicate that, in the presence of uncertainty in timing information of messages, the new methodology is more effective in detecting RT faults when compared to our previous methodology (i.e., TSSTM) and also test cases based on an operational profile.