Conformance testing is still the main industrial validation technique for telecommunication protocols. The automatic construction of test cases based on the model approach is hindered by the state explosion problem. In [BFG01], a method is described that minimizes the impact of state explosion by reconsidering the test case generation at a higher level and by taking advantage of some static analysis techniques, in particular the slicing techniques. The specification is simplified by pipelining a set of three modules, each one implementing a different slicing technique.