A method and apparatus is described for generating a test case for an application or system modelled using a Stochastic Automata Network model. The method contemplates the inclusion of a plurality of automata and including the steps of: (a) setting an initial global state as the current global state, wherein a global state comprises a set of local states each corresponding to one of the automata; (b) creating a record of the initial global state; (c) selecting an event from a set of events that can be applied to the current global state; creating record of the selected event; (e) identifying those of the automata affected by the selected event and updating the current global state by updating the states of the affected automata; (f) creating a record of the current global state; and repeating steps (c) to (f) until a termination condition is satisfied. The invention may also be used for the generation of test scripts. In terms of specific usage case, the invention may be used for software reliability testing and for fault-tolerance measurements.