Increasing numbers of software developers are using the Unified Modeling Language (UML) and associated visual modeling tools as a basis for the design and implementation of their distributed, component-based applications. At the same time, it is necessary to test these components, especially during unit and integration testing. At Siemens Corporate Research, we have addressed the issue of testing components by integrating test generation and test execution technology with commercial UML modeling tools such as Rational Rose; the goal being a design-based testing environment. In order to generate test cases automatically, developers first define the dynamic behavior of their components via UML Statecharts, specify the interactions amongst them and finally annotate them with test requirements. Test cases are then derived from these annotated Statecharts using our test generation engine and executed with the help of our test execution tool. The latter tool was developed specifically for i...