Testing of software is a time-consuming activity which requires a great deal of planning and resources. Model-based testing is gaining importance as a research issue. In scenario-based testing, test scenarios are used for generating test cases, test drivers etc. UML is widely used to describe analysis and design specifications of software development. UML models are important source of information for test case design. UML activity diagrams describe the realization of the operation in design phase and also support description of parallel activities and synchronization aspects involved in different activities perfectly. In this paper we generate test scenarios from activity diagrams, which achieve test adequacy criteria perfectly. Finally we generate test cases by analyzing the respective sequence and class diagrams of each scenario, which achieves maximum path coverage criteria. Also in our approach, the cost of test model creation is reduced as design is reused.