Many innovations at cropping system level impact the whole farm system by changing the flow of farm resources across farm activities. Using farm models has increasingly been proposed for assessing the feasibility of prototypes of cropping systems at farm level, and evaluating their impacts on household food production, farm income, and the environment. Such models are often called bio-economic model as a way to stress the mixing of knowledge about the biophysical and economic aspects of farming (Janssen & van Ittersum, 2007; Thornton & Herrero, 2001). A priori, one should not expect accurate predictions from these coupled bio-economic models, because of their complexity and the difficulty of measuring certain key input variables, such as labour availability for the different farm and off-farm activities, family income, and intra-farm consumption of agricultural products. This type of models can rather be used to explore ‘what if’ scenarios and to understand their outcomes including their inevitable uncertainty. In this paper, we review our experience with bio-economic farm models as virtual test benches for evaluating “cropping systems ideotypes” (CSI), i.e. idealized cropping systems proposed as alternatives to existing cropping systems, for increasing farm income and production or for reducing negative impacts of farming on the environment. Six published case studies are used. The objective is to examine to what extent the models developed fulfilled their purpose of evaluating prototypes of cropping systems for farming systems design.