Minimum-cost synchronizable test sequence generation via the duplexU digraph

A test sequence generation method is proposed for testing the conformance of a protocol implementation to its specification in a remote testing system, taking both external synchronization and input/output operation costs into consideration. The method consists of a set of transformation rules that constructs a duplexU digraph from a given finite state machine (FSM) representation of a protocol specification and a heuristic algorithm that finds a rural postman tour in the duplexU digraph to generate a synchronizable test sequence utilizing multiple UIO sequences. If the protocol satisfies a specific property, the heuristic algorithm yields a minimum-cost test sequence. The X.25 DTE and ISO Class 0 Transport protocols are proved to possess this specific property. otherwise, the heuristic algorithm yields a test sequence whose cost is within a bound from the cost of the minimum-cost test sequence. The bound for the test sequence generated from the Q.931 Network-side protocol is shown to be the cost sum of an input/output operation and an external synchronization operation