Abstract: Object-oriented testing activity is indispensable to the development of object-oriented software. For the features of object-oriented software, the traditional testing technology can not be applied directly to object-oriented software efficiently, the test strategy and test methods must be adapted. Based on program partition mechanism, a new object-oriented testing coverage metrics, named object-oriented segment coverage, is proposed in this paper. The object-oriented segment coverage is superior to traditional structural coverage metrics which take no account of the effect of object-oriented features on object-oriented testing coverage. And the architecture of an implemented object-oriented software testing tool of good generality and reusability for many different object-oriented languages is described.