MAFALDA is a generic experimental environment that is intended to support, for several microkernel candidates, both objectives of characterization of the failure modes in the presence of injected faults (internal or external) and of the incorporation of wrappers to improve these failure modes. After a short classification of current microkernel architectures and of their interactions between the application layer and the microkernel functional components, the paper presents the main features of MAFALDA with a focus on the fault injection and wrapping modules. The implementation of these modules is then described distinguishing the two main modes of interactions identified (library-based or trap-based). Some experimental results are presented that show the usefulness of the tool. The paper concludes by a summary of the main characteristics of MAFALDA and a brief discussion of our future work.