Improving test coverage for UML state machines using transition instrumentation

We discuss the problem of generating test suites from UML state machines and present a method to extend the capabilities of existing automated test case generators. Current tools provide only a limited coverage for different testing objectives. We argue that a better coverage can be achieved by instrumenting transitions, and performing an appropriate pre - and postprocessing. We describe the necessary enhancements of the UML model and demonstrate our method on a simple example. We further report on an industrial case study where we successfully applied our method for generating a validation test suite for a safety-relevant communication protocol.