The priority inversion problem was detected two decades ago (B.W. Lampson and D.D. Redell, 1980). The decisive ideas to cope with this problem were published one decade ago (1990). In the meantime, the vendors of operating systems and run-time systems have occupied this topic in providing certain protocols in order to avoid priority inversion. However, on closer inspection, there are considerable differences in the usage and the results of the various protocol interfaces. This is really pitiful in the scope of real time systems, because the application programmer wants to rely on certain predictability criteria, depending only on the kind of protocol used. Hence, we propose test suites to check the degree of conformance between the protocol proposed in the literature and the one implemented in a certain environment. Index Terms: conformance testing; protocols; real-time systems; scheduling; conformance testing; priority inheritance protocols; priority inversion problem; operating systems; run-time systems; protocol interfaces; real time systems; application programmer; predictability criteria; test suites