W-method for Hierarchical and Communicating Finite State Machines

The W-method is one of the most general and widely used methods for generating tests from a finite state machine (FSM). The paper shows how the W-method can be used to generate test sequences from a hierarchical FSM and also from a system of communicating FSMs in which the communication is one-directional. By refining test suites in parallel with the specification and using a divide and conquer strategy, the size of the test data is considerably reduced in comparison to the case in which tests are derived directly from the final specification.