This paper describes our experiences of the methods used by novice software testers to test their own programs, as well as their perception of the classification-tree method, which is a black box testing method first introduced by Grochtmann and Grimm. We conducted two case studies involving novice software testers. The subjects in the first study possessed one-year working experience while those in the second study had a wider range of working experiences. Both studies found that white box testing methods were initially far more popular than black box methods, but the majority of the subjects were convinced of the benefits of the classification-tree method after they had learned and used it. About two-third of them indicated their preference of the classification-tree method over the methods they originally used.