The development of economic and hybrid vehicles is only possible with complex systems to control the energy management and engine. The amount of embedded electronics and software to realize these systems increases continuously, and hence the complexity of the integration. The functional validation and testing of these systems is of increasing importance, as these systems have an increasing impact on other systems like comfort and safety functionalities. So there is a need for thourough testing. However, exhaustive testing is not possible as testing in industry is limited by time and resources. So a method is needed to derive systematically the most significant test cases in order to be able to assess the behavior of the system. We applied test models to accomplish this task. A Timed Usage Model served as a formal requirement specification and was the basis for following test activities. The model provides the possibility to describe timing and data dependencies of the system to be tested. The test planning and test case generation was supported by the models. The appliance of models allowed the systematic generation of test cases and the assessment of the significance of the conducted test activities with respect to the coverage of requirements.