A method for connecting an input/output interface of a testing device equipped for testing a control unit to a model of a technical system present in the testing device. The interface connects the control unit to be tested or connects a technical system to be controlled; the model to be connected to the input/output interface is a model of the technical system to be controlled or a model of the control unit to be tested. The testing device has a plurality of input/output functions connected to the model and provides an interface hierarchy structure and a function hierarchy structure. The method has an automatic configuration of compatible connections between the interface hierarchy structure and the function hierarchy structure so that the model present in the testing device communicates through the compatible connections with the control unit to be tested or the technical system to be controlled.