Abstract: The Controlled Markov Chain(CMC) model for software testing discussed in most works at present is obtained from a series of assumptions,and partial of the assumptions have been specialized,which makes the scope of application of these models were comparatively small. And thus these models deviate from practical application. According to the software cybermetics, this article provided an improved CMC model with cost constraints by introducing a series of new transformation of limit condition. I}his model eliminates some of the defects of existing models. Meanwhile, the model can reach a balance in efficiency, complexity and applicability. In order to verify the effectiveness of the model, a new optimal testing strategy for software defects was designed according to the newly provided model. Through a simulation experiment, the strategy was compared with the traditional random testing strategy. The results show that our improved CMC model has high applicability and effectiveness.

Key words: Software cybernetics, Software defects test, Optimal testing strategy, Controlled Markov chain