A simulator and a method for testing a control device function of a control device of a vehicle. The vehicle includes various environmental sensors, such as radar, a camera, and a radio receiver, which serve as inputs to the control device function of the control device. A corresponding simulation utilizing a vehicle model sensor models, and an environmental model is executed in a distributed fashion via a plurality of computing units and a memory of a simulator. The simulation utilizing the vehicle model, the sensor models, and the environmental model provides inputs to the control device function. Moreover, the simulation utilizing these models is started synchronously on the computing units, wherein data exchange occurs amongst the memory and the multiple computing units.