A method is provided for testing a computer system, which system includes an interface supporting connection to one or more hardware devices. The method comprises initially performing a plurality of discrete software test processes in a first order of performance. For each test process, by reference to the said interface, the hardware device interactions occasioned by each said test process are recorded. Subsequently the said test processes are run in a second order of performance, which second order is derived from the record of hardware device interactions. A computer system configured to implement the method is also provided.