We present in this article a way to produce test suites applied to the POSIX mini-challenge based on a behavioral model of a file system manager written in UML/OCL. We illustrate the limitations of a fully automated test generation approach, which justifies the use of test scenarios as a complement to a functional testing approach. Scenarios are expressed through regular expressions describing sequences of operations, possibly punctuated by intermediate states that have to be reached by the execution of the model. Scenarios are unfolded into extended sequences of operations that are played on the model using symbolic animation techniques. We experimented our approach by testing the conformance of two different file systems w.r.t. the POSIX standard: a recent Linux distribution and a customized Java implementation of POSIX used to evaluate the relevance of our approach and its complementarity with a structural test generation approach.