Robustness testing is a part of the validation process which consists in testing the behavior of a system implementation under exceptional execution conditions in order to check if it still fulfills some robustness requirements. We propose a theoretical framework for model-based robustness testing together with an implementation within the If validation environment. Robustness test cases are generated from both a (partial) operational specification and an abstract fault model. This generation technique is inspired from the ones used in (classical) conformance testing – already implemented in several tools. This framework is illustrated on a small example.