The invention relates to a method for evaluating an application for controlling a process within an automation system. The application is stored within a controller, and at least two versions of it are present within the controller. The method comprises the steps of: inputting to the different versions of the application an input signal obtained from the process; executing, in the controller, tasks based on this input signal for the different versions; generating a report comprising comparisons of the outputs from the different versions of the application; and evaluating, based on the generated report, the version(s) not used for controlling the process. An improved way of revising an automation system is thereby achieved. The invention also relates to such controller and an automation system.