Generalizing the DS-Methods for Testing Non-Deterministic FSMs

Abstract

There exists a significant body of work devoted to so-called complete tests which guarantee the detection of all the faults in a given fault domain. Several methods for generating complete tests for finite state machines (FSMs) which are based on a distinguishing sequence (DS) have been proposed. These methods even if extended to use adaptive DSs apply only to deterministic FSMs and the question arises whether they can be extended to non-deterministic FSMs to test for trace inclusion. In this paper, we generalize the notion of DS to a so-called total state separator, which is an adaptive experiment distinguishing states in any FSM that is trace included into the specification FSM. We then propose a method to test non-deterministic FSMs for trace inclusion. State separator is a key means of the proposed method, which has two phases: in the first phase, a preset test is constructed, which should be repeatedly applied to a non-deterministic implementation, thus requiring its resetting; in the second phase, the implementation is tested online and no reset is required. To the best of our knowledge, this is the first method which tests non-deterministic FSMs for the trace inclusion conformance relation, while avoiding resetting implementations to re-execute tests for transition verification.