MUPPAAL: Reducing and Removing Equivalent and Duplicate Mutants in UPPAAL

Mutation Testing (MT) is a test quality assessment technique that creates mutants by injecting artificial faults into the system and evaluating the ability of tests to distinguish these mutants. We focus on MT for safety-critical Timed Automata (TA). MT is prone to equivalent and duplicate mutants, the former having the same behaviour as the original system and the latter other mutants. Such mutants bring no value and induce useless test case executions. We propose MUPPAAL, a tool that: (1) offers a new operator reducing the occurrence of mutant duplicates; (2) an efficient bisimulation algorithm removing remaining duplicates; (3) leverages existing equivalence-avoiding mutation operators. Our experiments on four UPPAAL case studies indicate that duplicates represent up to 32% of all mutants and that the MUPPAAL bisimulation algorithm can identify them more than 99% of the time.