Abstract: Testing activity is indispensable to the development of object oriented software.Much research has been done on object oriented analysis,design and programming languages.Yet relatively little work has been done to address the question of how object oriented programs should be tested.The impact of object orientation on testing is studied in this paper.Various testing methods proposed in the literature,such as specification based testing,program based testing,and the integration of testing with development process are surveyed.Directions of future research are also discussed.