Current requirements of ecology and mobility are at the basis of the development of less polluting vehicles. In most of the cases, these vehicles need a clever and optimized energy management, which can be reached thanks to a more complex electronic embedded system. That is why, a special care on electronics reliability is required to ensure a good product quality. In this paper, we will focus on a systematic reasoning to obtain a suited test bench for covering the verification of a complete set of embedded electronics functional specification of a hybrid powertrain. The HIL (Hardware In the Loop) test bench enables the control unit environment in real time to be simulated and their closed loop behavior in wished situations to be studied. Based on control unit and system specifications, the method describes how to define the HIL platform in terms of hardware interface and internal behavior (models).