Traceback: A Fault Localization Technique for Molecular Programs

Fault localization is essential to software maintenance tasks such as testing and automated program repair. Many fault localization techniques have been developed, the most common of which are spectrum-based. Most techniques have been designed for traditional programming paradigms that map passing and failing test cases to lines or branches of code, hence specialized programming paradigms which utilize different code abstractions may fail to localize well. In this paper, we study fault localization in the context of a class of programs, molecular programs. Recent research has designed automated testing and repair frameworks for these programs but has ignored the importance of fault localization. As we demonstrate, using existing spectrum-based approaches may not provide much information. Instead we propose a novel approach, Traceback, that leverages temporal trace data. In an empirical study on a set of 89 faulty program variants, we demonstrate that Traceback provides between a 32-90% improvement in localization over reaction-based mapping, a direct translation of spectrum-based localization. We see little difference in parameter tuning of Traceback when all tests, or only code-based (invariant) tests are used, however the best depth and weight parameters vary when using specification based tests, which can be either functional or metamorphic. Overall, invariant-based tests provide the best localization results (either alone or in combination with others), followed by metamorphic and then functional tests.