Effective Fault Localization of Automotive Simulink Models: Achieving the Trade-Off between Test Oracle Effort and Fault Localization Accuracy

One promising way to improve the accuracy of fault localization based on statistical debugging is to increase diversity among test cases in the underlying test suite. In many practical situations, adding test cases is not a cost-free option because test oracles are developed manually or running test cases is expensive. Hence, we require to have test suites that are both diverse and small to improve debugging. In this paper, we focus on improving fault localization of Simulink models by generating test cases. We identify four test objectives that aim to increase test suite diversity. We use four objectives in a search-based algorithm to generate diversified but small test suites. To further minimize test suite sizes, we develop a prediction model to stop test generation when adding test cases is unlikely to improve fault localization. We evaluate our approach using three industrial subjects. Our results show (1) expanding test suites used for fault localization using any of our four test objectives, even when the expansion is small, can significantly improve the accuracy of fault localization, (2) varying test objectives used to generate the initial test suites for fault localization does not have a significant impact on the fault localization results obtained based on those test suites, and (3) we identify an optimal configuration for prediction models to help stop test generation when it is unlikely to be beneficial. We further show that our optimal prediction model is able to maintain almost the same fault localization accuracy while reducing the average number of newly generated test cases by more than half.