Biblio

We present NonDex, a tool for detecting and debugging wrong assumptions on Java APIs. Some APIs have underdetermined specifications to allow implementations to achieve different goals, e.g., to optimize performance. When clients of such APIs assume stronger-than-specified guarantees, the resulting client code can fail. For example, HashSet’s iteration order is underdetermined, and code assuming some implementation-specific iteration order can fail. NonDex helps to proactively detect and debug such wrong assumptions. NonDex performs detection by randomly exploring different behaviors of underdetermined APIs during test execution. When a test fails during exploration, NonDex searches for the invocation instance of the API that caused the failure. NonDex is open source, well-integrated with Maven, and also runs from the command line. During our experiments with the NonDex Maven plugin, we detected 21 new bugs in eight Java projects from GitHub, and, using the debugging feature of NonDex, we identified the underlying wrong assumptions for these 21 new bugs and 54 previously detected bugs. We opened 13 pull requests; developers already accepted 12, and one project changed the continuous-integration configuration to run NonDex on every push. The demo video is at: https://youtu.be/h3a9ONkC59c

Regression test selection (RTS) aims to reduce regression testing time by only re-running the tests affected by code changes. Prior research on RTS can be broadly split into dy namic and static techniques. A recently developed dynamic RTS technique called Ekstazi is gaining some adoption in practice, and its evaluation shows that selecting tests at a coarser, class-level granularity provides better results than selecting tests at a finer, method-level granularity. As dynamic RTS is gaining adoption, it is timely to also evaluate static RTS techniques, some of which were proposed over three decades ago but not extensively evaluated on modern software projects. This paper presents the first extensive study that evaluates the performance benefits of static RTS techniques and their safety; a technique is safe if it selects to run all tests that may be affected by code changes. We implemented two static RTS techniques, one class-level and one method-level, and compare several variants of these techniques. We also compare these static RTS techniques against Ekstazi, a state-of-the-art, class-level, dynamic RTS technique. The experimental results on 985 revisions of 22 open-source projects show that the class-level static RTS technique is comparable to Ekstazi, with similar performance benefits, but at the risk of being unsafe sometimes. In contrast, the method-level static RTS technique performs rather poorly.