Testing Timed Nondeterministic Finite State Machines with the Guaranteed Fault Coverage

Abstract

The behavior of many systems can be properly described by taking into account time constraints, and this motivates the adaptation of existing Finite State Machine (FSM)-based test derivation methods to timed models. In this paper, we propose a method for deriving conformance tests with the guaranteed fault coverage for a complete possibly nondeterministic FSM with a single clock; such Timed FSMs (TFSMs) are widely used when describing the behavior of software and digital devices. The fault domain contains every complete TFSM with the known upper bounds on the number of states and finite boundary of input time guards. The proposed method is carried out by using an appropriate FSM abstraction of the given TFSM; the test is derived against an FSM abstraction and contains timed input sequences. Shorter test suites can be derived for a restricted fault domain, for instance, for the case when the smallest duration of an input time guard is larger than two. Moreover, the obtained test suites can be reduced while preserving the completeness, when all input time guards of the specification and an implementation under test are right closed (or all guards are left-closed). Experiments are conducted to study the length of test suites constructed by different methods.