Resilient farming systems are systems wich have survived from period to period. When we consider elements relative to the farmer, that is to say choices, decisions and learning processes, we use, like some other authors, the concept of flexibility. Socio-technical systems are supposed to be flexible when they have the capacity to respond or to conform to new or changing situations. The research team of Mirecourt (INRA) prototypes farming systems focusing on agro-environmental sustainability. Prototyping is orgnaised around a pluriannual experimentation at the system scale. Such experiment might be well adapted to prototype resilient farming systems and decision rules by studying the flexibility of the whole system together with the plasticity of the biological elements within the system (crops, animals...). Thus prototyping could be a good help to create applied knowledge on innovative systems.