AbstractEvaluation of the adequacy of a test set consisting of one or more test cases is a problem oftes encountered in software testing environments. Two test adequacy criiteria are considered, namely the data flow based all‐uses criterion and a mutation based criterion. An empirical study was conducted to compare the ‘difficulty’ of satisfying the two criteria and their costs. Similar studies conducted in the past are discussed in the light of this study. A discussion is also presented of how and why the results of this study, when viewed in conjunction with the results of earlier comparisons of testing methods, are useful to a software test