Testing and incremental conformance testing of timed state machines

Abstract

We present methods for testing and incremental testing of systems modeled as finite state machines with timeouts (TFSMs). For testing, we establish an appropriate fault model and show how a complete test suite can be derived for a given TFSM specification using traditional FSM-based test derivation approaches considering an untimed FSM abstraction of the given specification. In addition, we consider reducing the cost of testing a modified or an evolving TFSM specification by the selection of appropriate incremental test suites that can verify whether the modified parts of a modified specification are correctly implemented in a corresponding implementation under test. In particular, we define the incremental testing problem for TFSMs and investigate appropriate fault models that can be used for incremental test derivation and accordingly propose related test selection algorithms. According to conducted experiments length and run time (sum of time delays) of obtained test suites are much lower than their theoretic upper bounds; in some cases, these bounds are linear. In addition, for incremental testing, when the modified part is up to 20% of the whole specification, length and run time of incremental test suites are at least twice as less than those obtained using the whole modified specification.