Abstract: A verification apparatus and method are disclosed for testing a device or system which is operable in a number of states through which it can transition in a multiplicity of different sequences. The method and apparatus disclosed include a set of functional modules which correspond to the states of the device or system under test and which may be activated in a large number of pseudorandom sequences. Each time a module of the verification apparatus is activated it causes the device or system under test to transition to the corresponding state. Thus, when the functional modules of the verification apparatus are activated in a given sequence, the corresponding states of the device or system under test are called in the same sequence.