Exploring Test Suite Diversification and Code Coverage in Multi-Objective Test Case Selection

Test case selection is a classic testing technique to choose a subset of existing test cases for execution, due to the limited budget and tight deadlines. While `code coverage' is the state of practice among test case selection heuristics, recent literature has shown that `test case diversity' is also a very promising approach. In this paper, we first compare these two heuristics for test case selection in several real-world case studies (Apache Ant, Derby, JBoss, NanoXML and Math). The results show that neither of the two techniques completely dominates the other, but they can potentially be complementary. Therefore, we next propose a novel approach that maximizes both code coverage and diversity among the selected test cases using NSGA-II multi- objective optimization, and the results show a significant improvement in fault detection rate. Specifically, sometimes this novel approach detects up to 16\%(Ant), 10\%(JBoss), and 14\% (Math) more faults compared to either of coverage or diversity-based approaches, when the testing budget is less than 20\% of the entire test suite execution cost.