PreInfer: Automatic Inference of Preconditions via Symbolic Analysis

When tests fail (e.g., throwing uncaught exceptions), automatically inferred preconditions can bring various debugging benefits to developers. If illegal inputs cause tests to fail, developers can directly insert the preconditions in the method under test to improve its robustness. If legal inputs cause tests to fail, developers can use the preconditions to infer failure-inducing conditions. To automatically infer preconditions for better support of debugging, in this paper, we propose PREINFER, a novel approach that aims to infer accurate and concise preconditions based on symbolic analysis. Specifically, PREINFER includes two novel techniques that prune irrelevant predicates in path conditions collected from failing tests, and that generalize predicates involving collection elements (i.e., array elements) to infer desirable quantified preconditions. Our evaluation on two benchmark suites and two real-world open-source projects shows PREINFER's high effectiveness on precondition inference and its superiority over related approaches.