An application program that describes processing of a workpiece by the machine tool in form of instruction steps is disclosed. A computer executes the application program and step-by-step determines based on a simulation program machine-dependent control commands for a controller. The machine-dependent control commands depend on a virtual time base that is independent of an actual time base. The computer determines based on a computer-internal model of the machine tool and the determined machine-dependent control commands expected actual states of the machine tool, thereby simulating execution of the machine-dependent control commands by the machine tool. The simulation program is implemented as control software in the controller.