Efficient Guiding Strategies for Testing of Temporal Properties of Hybrid Systems

Techniques for testing cyberphysical systems (CPS) currently use a combination of automatic directed test generation and random testing to find undesirable behaviors. Existing techniques can fail to efficiently identify bugs because they do not adequately explore the space of system behaviors. In this paper, we present an approach that uses the rapidly exploring random trees (RRT) technique to explore the statespace of a CPS. Given a Signal Temporal Logic (STL) requirement, the RRT algorithm uses two quantities to guide the search: The first is a robustness metric that quantifies the degree of satisfaction of the STL requirement by simulation traces. The second is a metric for measuring coverage for a dense state-space, known as the star discrepancy measure. We show that our approach scales to industrial-scale CPSs by demonstrating its efficacy on an automotive powertrain control system.