Test suites developed for complex software systems contain thousands of test cases. Keeping track on the test coverage and changing the test suite as the system requirements evolve can consume significant efforts. Testers have to implement or generate test scripts containing thousands of isolated executable test cases. Each single test case should be so simple enough so that test results can be easily evaluated. Often it makes code duplication in the test code unavoidable. If every test script is written by a human the costs for test code maintenance by specification changes can explode. ...