1. A radio device testing system comprising: at least one radio device ( 16 ) having a software radio stack ( 40 ) through which radio messages comprising data are processed in accordance with a predetermined radio protocol, and test control means ( 10 ) for controlling and monitoring the testing of said at least one radio device via a link ( 30 ) therebetween, characterised in that perturbation means ( 38 ) linked to said stack and to said control means is provided and where, under control of said test control means, said stack perturbation means perturbs an aspect of said radio stack processing.