Can Higher-Order Mutants Improve the Performance of Mutation-Based Fault Localization?

First-order mutants (FOMs) have been widely used in mutation-based fault localization (MBFL) approaches and have achieved promising results in single-fault localization scenarios (SFL-scenario). Higher-order mutants (HOMs) are proposed to simulate complex faults and can be applied in MBFL theoretically for multiple-fault localization scenarios (MFL-scenario). However, whether HOMs can improve MBFL’s performance is not investigated and the effectiveness is not thoroughly evaluated. In this empirical study, we investigate the impact of HOMs on the performance of MBFL in SFL-scenario and MFL-scenario. The experiments on two real-world benchmarks reveal that 1) 2-HOMs can help improve the MBFL performance in SFL-scenarios; 2) in MFL-scenarios, both 2-HOMs and 3-HOMs can achieve better performance than FOMs; and 3) huge computational cost cannot be ignored in the practice of HOMs. Therefore, effective methods to reduce the number of HOMs for future MBFL studies should be considered.