The successful application of model-based testing (MBT) heavily relies on constructing a complete and coherent model of a system. This implies that inconsistency, incompleteness, or inaccuracy due to human error bear significant consequences. We propose a formal framework for MBT which we call AHR: agile, human-centred and refinement- oriented. AHR captures an iterative construction of models and test plans, as well as supports refinements at different levels of abstraction.