Employing second-order mutation for isolating first-order equivalent mutants

The equivalent mutant problem is a major hindrance to mutation testing. Being undecidable in general, it is only susceptible to partial solutions. In this paper, mutant classification is utilised for isolating likely to be first-order equivalent mutants. A new classification technique, Isolating Equivalent Mutants (I-EQM), is introduced and empirically investigated. The proposed approach employs a dynamic execution scheme that integrates the impact on the program execution of first-order mutants with the impact on the output of second-order mutants. An experimental study, conducted using two independently created sets of manually classified mutants selected from real-world programs revalidates previously published results and provides evidence for the effectiveness of the proposed technique. Overall, the study shows that I-EQM substantially improves previous methods by retrieving a considerably higher number of killable mutants, thus, amplifying the quality of the testing process.