1. A method for analyzing an execution of a predetermined program flow on a physical computer system which has a plurality of interacting physical hardware units, comprising the following steps: replicating a functionality of a physical hardware unit as functionality of a virtual hardware unit in order to develop at least part of a virtual computer system which corresponds to the physical computer system; executing the program flow a first time using the replicated functionality of the virtual hardware unit, and monitoring a first execution behavior of the program flow; executing the program flow a second time using a varied functionality of the virtual hardware unit, and monitoring a second execution behavior of the program flow; and comparing the first execution behavior with the second execution behavior in order to identify an execution behavior change.