There are some features in object-oriented software

such as classes

encapsulation

inheritance

and dynamic connections.They make the division of object-oriented testing procedures and the choice of strategy different from traditional testing ideas.According to the characteristics of object-oriented software

the paper adopts the methods based on models for testing software and adds OCL(Object Constraints Language)constraints for sequence diagram of UML(United Model Language)design model and tests interaction among classes.The paper proposes the algorithm for generating EG(Execution Graph)and transforms SD(Sequence Diagram) to EG

and SD is constrainted by OCL for testing interaction among classes.In this algorithm

the testing problem for four major combined fragments including alt

loop

opt

break in the new features

and their nesting among them and the polymorphism

will be solved in sequence diagram of UML 2.0.In order to get the smallest complete test pathes

strategy for traversing EG and algorithm for generating test paths are presented.Finally

the paper proposes algorithm for determining test scenarios by testing pathes

deleting invalid scenarios by OCL constraints

and generating test cases.Experimental validation shows that our solution can test software based on UML sequence diagram and OCL.