A key feature in fault injection (FI) based validation is identifying the relevant test cases to inject. This problem is exacerbated at the protocol level where the lack of detailed fault distributions limits the use of statistical approaches in deriving and estimating the number of test cases to inject. In this paper we develop and demonstrate the capabilities of a formal approach to protocol validation, where the deductive and computational analysis capabilities of formal methods are shown to be able to identify very specific test cases, and analytically identify equivalence classes of test cases.