Experimental Evaluation of A New Ranking Formula for Spectrum based Fault Localization

Spectrum-Based Fault Localization (SBFL) uses a mathematical formula to determine a suspicion score for each program element (such as a statement, method, or class) based on fundamental statistics (e.g., how many times each element is executed and not executed in passed and failed tests) taken from test coverage and results. Based on the calculated scores, program elements are then ordered from most suspicious to least suspicious. The elements with the highest scores are thought to be the most prone to error. The final ranking list of program elements aids developers in debugging when looking for the source of a fault in the program under test.

In this paper, we present a new SBFL ranking formula that enhances a base formula by  ranking code elements slightly higher than others that are executed by more failed tests and less passing ones. Its novelty is that it breaks ties between the elements that share the same suspicion score of the base formula. Experiments were conducted on six single-fault programs of the Defects4J dataset to evaluate the effectiveness of the proposed formula. The results show that our new formula when compared to three widely-studied SBFL formulas, achieved a better performance in terms of average ranking. It also achieved positive results in all of the Top-N categories and increased the number of cases where the faulty element became the top-ranked element by 13–23%.

Keywords:     Debugging, fault localization, spectrum-based fault localization,  formulas, ranking list.