A method for testing software of an electronic control unit of a vehicle includes, in a first step, executing a driving cycle, whereby input quantities and output quantities of the electronic control unit are recorded. In an additional step, the driving cycle in accordance with the first step is repeated without once again executing the driving cycle with the vehicle on the testing device so that additional output quantities are made available. It is ascertained that the software comprises a function that recognizes whether a driving cycle is being executed with the vehicle, based on there being a deviation between at least one output quantity that had been recorded in the first step and the corresponding output quantity provided in accordance with the additional step. Based thereon, a function of the electronic control unit is excluded from being further developed or processed during a subsequent development step.