A test device for testing at least a portion of a virtual control unit with a simulation environment in a simulator, having the virtual control unit and the simulation environment. The virtual control unit has at least one software component with an external data interface. The simulation environment has a data interface for indirect data exchange with the virtual electronic control unit. A reduced dependency between the virtual control unit and the simulation environment with the result that electrical fault simulation with virtual electronic control units is possible in a simpler way, is achieved in that a virtual control unit pin module and a virtual manipulation unit are additionally provided between the virtual control unit and the simulation environment, the two units transmit a virtual physical control unit signal through a virtual control unit pin of the virtual electronic control unit pin module. The virtual manipulation unit outputs a manipulated virtual physical control unit signal.