Generating Efficient Test Sets with a Model Checker

It is well-known that counterexamples produced by model checkers can provide a basis for automated generation of test cases. However, when this approach is used to meet a coverage criterion, it generally results in very inefficient test sets having many tests and much redundancy. We describe an improved approach that uses model checkers to generate efficient test sets. Furthermore, the generation is itself efficient, and is able to reach deep regions of the statespace. We have prototyped the approach using the model checkers of our SAL system and have applied it to model-based designs developed in Stateflow. In one example, our method achieves complete state and transition coverage in a Stateflow model for the shift scheduler of a 4-speed automatic transmission with a single test case.