New approaches for passive testing using an Extended Finite State Machine specification

This paper presents two new approaches for passive testing using an Extended Finite State Machine (EFSM) specification. The state of the art of passive testing shows us that all the methods for detection of errors based on EFSMs try to match the trace to the specification. Indeed, one searches a state succession in the specification machine that is able to generate the trace observed on the implementation. Using this approach, processing is performed on the specification and the trace remains in the background since no operation is applied to it. This made us realise that focusing our efforts on the trace could be beneficial and has given as result two approaches presented in this paper that extract information from the specification and then work on the trace. Thus, they take a different direction than the previous methods. We first present an approach to test traces by using invariants resulting from the specification. We formally define these invariants and we see how to extract them. We also discuss their ability to detect errors appearing in the implementation. This approach is able to test the data flow, but not in a very satisfactory way. This is the reason for a second approach seeking to apply a set of constraints to the trace. We develop in detail its principles. Both approaches are applied to a Simple Connection Protocol (SCP) and the results of preliminary experiments are presented. q 2003 Elsevier B.V. All rights reserved.