A theoretical analysis on cloning the failed test cases to improve spectrum-based fault localization.

•The cloning of failed test cases is studied in three fault-localization scenarios.•The accuracy of 33 popular techniques is evaluated, using four expense metrics.•On about two thirds of them, statistically significant improvements are observed.•On about one third of them, the accuracy is observed and proved unaffected.•Accuracy improvements on 19 of them are theoretically confirmed in one scenario.