This paper investigates the impact of state on robustness testing, by enhancing the traditional approach with the inclusion of the OS state in test cases definition. We evaluate the relevance of OS state and the effects of the proposed strategy through an experimental campaign on the file system of a Linux-based OS, to be adopted by Finmeccanica for safety-critical systems in the avionic domain. Results show that the OS state plays an important role in testing those corner cases not covered by traditional robustness testing