Software testing and maintenance being interleaved phases span more in software life cycle. The efforts to minimize this span rely obviously on testing when maintenance is natural. The features of Object-Oriented (OO) software systems, when compared to the classical systems, claim much reducing the maintenance costwithout necessarily thepossibility of maintenance itself. It is natural that even such systems evolve due to many reasons. Though the specific reasons leading to the maintenance differ, the general rationale behind maintenance is to enhance the life-cycleand possibly the value of the existing system. Hence testing effort is more natural and significant even then. Moreover, the salient features of OO software systems furtherance the testing span despite their claim on maintenance. However, the availability of classical OO software metrics aid better early quality testing of OO systems. They exploit the critical parts of OO software systems thereby offering timely, thorough, and effective assurance. However there is not yet a common metric model in this regard. On the other hand, it is expected that the evolved model-based OO software metrics help define the subjective features more objectively facilitating users to perform metrics klockor kopior activities. The conflation of both classical and model-based metrics mutually alleviates their limitations and brings more synergy in reducing the test costs of OO software systems.