Abstract: Object-oriented software is implemented by the classes and the association between its classes. Class testing is the key to objectoriented software testing. The paper studies a method of class level software testing that how the state diagram containing hierarchy and concurrent structure is transformed into extended finite state machine(EFSM)and obtains the corresponding test spanning tree, then uses the test spanning tree to produce software testing data. Experiments show that the test method is feasible and effective, and better results could be achieved in practice.

Key words: state diagram, class level software testing, EFSM