 In contrast to traditional mutation testing where mutant faults are generated and injected into the code description of the model, application of a series of newly defined mutation operators directly to the model properties rather than to the model code has also been investigated.Mutant properties that are generated from the initial properties (or test cases) and validated by the model checker should be considered as new properties that have been missed during the initial verification procedure.Therefore, adding these newly identified properties to the existing list of properties improves the coverage metric of the formal verification and consequently lead to a more reliable design.