Nowadays test engineers typically use two strategies for the design of test cases. First, test cases are designed related to some kind of structural coverage criteria. Second, test cases are created by having a specific fault model in mind. In this paper we evaluate these two supplementary techniques for test purpose design. We present a heuristic algorithm for the extraction of test cases from tgv's output, i.e., the test process. We discuss the problem of overlapping test purposes and illustrate improvements in terms of test execution time and in terms of number of test cases when minimizing this overlap. Furthermore, we evaluate different strategies for the generation of fault-based test purposes on our specification. For our evaluation, all extracted test cases are executed against a commercial and an open source implementation of a Session Initiation Protocol (SIP) Registrar.