Today component-based technologies play an important role in system development. However, although the technologies used to define, implement, and assemble components and systems of components have improved significantly over recent years, verification techniques have not yet caught up. Correctness and reliability of component-based systems are still often checked using traditional testing techniques. These techniques are unable to use the knowledge about the structure of the systems and its components. Therefore, an approach is needed to reduce the effort involved in system testing. Clearly, the best would be to automate large parts of the testing process. Built-in tests - tests that are packaged with components - are a good basis for such an approach.