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arXiv · 1611.07163

Will My Tests Tell Me If I Break This Code?

Rainer Niedermayr·Elmar Juergens·Stefan Wagner
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Abstract

Automated tests play an important role in software evolution because they can rapidly detect faults introduced during changes. In practice, code-coverage metrics are often used as criteria to evaluate the effectiveness of test suites with focus on regression faults. However, code coverage only expresses which portion of a system has been executed by tests, but not how effective the tests actually are in detecting regression faults. Our goal was to evaluate the validity of code coverage as a measure for test effectiveness. To do so, we conducted an empirical study in which we applied an extreme mutation testing approach to analyze the tests of open-source projects written in Java. We assessed the ratio of pseudo-tested methods (those tested in a way such that faults would not be detected) to all covered methods and judged their impact on the software project. The results show that the ratio of pseudo-tested methods is acceptable for unit tests but not for system tests (that execute large portions of the whole system). Therefore, we conclude that the coverage metric is only a valid effectiveness indicator for unit tests.

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Rainer Niedermayr, Elmar Juergens, Stefan Wagner. 2016-11-22. Will My Tests Tell Me If I Break This Code?. https://doi.org/10.1145/2896941.2896944

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