Enhancing test coverage by back-tracing model-checker counterexamples

The automatic detection of unreachable coverage goals and generation of tests for 'corner-case' scenarios is crucial to make testing and simulation based veri.cation more e.ective. In this paper we address the problem of coverability analysis and test case generation in modular and component based systems. We propose a technique that, given an uncovered branch in a component, either establishes that the branch cannot be covered or produces a test case at the system level which covers the branch. The technique is based on the use of counterexamples returned by model checkers, and exploits compositionality to cope with large state spaces typical of real applications.