Fatiha Zaïdi

Hit-or-Jump: An algorithm for embedded testing with applications to IN services

This paper presents a new algorithm, Hit-or-Jump, for embedded testing of components of communication systems that can be modeled by communicating extended finite state machines. It constructs test sequences efficiently with a high fault coverage. It does not have state space explosion, as is often encountered in exhaustive search, and it quickly covers the system components under test without being “trapped”, as is experienced by random walks. Furthermore, it is a generalization and unification of both exhaustive search and random walks; both are special cases of Hit-or-Jump. The algorithm has been implemented and applied to embedded testing of telephone services in an Intelligent Network (IN) architecture, including the Basic Call Service and five supplementary services.

Automatic Timed Test Case Generation for Web Services Composition

In order to specify the composition of Web services, WSBPEL was defined as an orchestrating language by an international standards consortium. In this paper, we propose a method to test composite Web service described in BPEL. As a first step, the BPEL specification is transformed into an Intermediate Format (IF) model that is based on timed automata, which enables modeling of timing constraints.We defined a conformance relation between two timed automata(of implementation and specification) and then proposed an algorithm to generate test cases. Test case generation is based on simulation where the exploration is guided by test purposes. The proposed method was implemented in a set of tools which were applied to a common Web service as a case study.

A Formal Framework for Service Orchestration Testing Based on Symbolic Transition Systems

The pre-eminent role played by software composition, and more particularly service composition, in modern software development, together with the complexity of workflow languages such as WS-BPEL have made composite service testing a topical issue. In this article we contribute to this issue with an automatic testing approach for WS-BPEL orchestrations. Compared to related work, we support WS-BPEL data computations and exchanges, while overcoming the consequential state explosion problem. This is achieved through the use of symbolic transition system models and their symbolic execution. Throughout the article, we illustrate our approach on a realistic medium-size example.

Cubicle: a parallel SMT-based model checker for parameterized systems: tool paper

Cubicle is a new model checker for verifying safety properties of parameterized systems. It implements a parallel symbolic backward reachability procedure using Satisfiabilty Modulo Theories. Experiments done on classic and challenging mutual exclusion algorithms and cache coherence protocols show that Cubicle is effective and competitive with state-of-the-art model checkers.

Timed Modeling of Web Services Composition for Automatic Testing

This paper presents the modeling of BPEL (timed) constructs by using a new formalism WS-TEFSM (Web Service Timed Extended Finite State Machine). A formal mapping of all BPEL constructs is proposed as well as a model that corresponds to the BPEL Web services composition. The WS-TEFSM formalism allows to deal with timing constraints, data variables, clocks and priority on transitions. To perform the transformation, we define a renaming function and an asynchronous product of all partial machine corresponding to the BPEL process sub-activities. This model is enriched by the addition of priorities on transitions, which permit to handle the termination of the BPEL process and its sub-activities, and by global variables, which are used in the management of events and faults. This transformation step is essential to ensure the test of Web services. A rigorous approach is crucial as we have to deal with complex systems that manage distribution, low-coupled nature and asynchronous behaviors.

Invariants for finite instances and beyond

Verification of safety properties of concurrent programs with an arbitrary numbers of processes is an old challenge. In particular, complex parameterized protocols like FLASH are still out of the scope of state-of-the-art model checkers. In this paper, we describe a new algorithm, called BRAB, that is able to automatically infer invariants strong enough to prove a protocol like FLASH. BRAB computes over-approximations of backward reachable states that are checked to be unreachable in a finite instance of the system. These approximations (candidate invariants) are then model checked together with the original safety properties. Completeness of the approach is ensured by a mechanism for backtracking on spurious traces introduced by too coarse approximations.

Checking the behavioral conformance of web services with symbolic testing and an SMT solver

Workflow-based service composition languages foster the rapid design and development of distributed applications. The behavioral verification of service Compositions has widely been addressed at design time, using modelchecking. Testing is a complementary technique when it comes to check the behavioral conformance of a service implementation with respect to its specification or to a user or a service need. In this paper we address this issue with an automatic approach based on symbolic testing and an SMT solver.

WebMov: A Dedicated Framework for the Modelling and Testing of Web Services Composition

This paper presents a methodology and a set of tools for the modelling, validation and testing of Web service composition, conceived and developed within the French national project WebMov. This methodology includes several modelling techniques, based mainly on some variations of Timed Extended Finite State Machines (TEFSM) formalism, which provide a formal model of the BPEL description of Web services composition. These models are used as a reference for the application of different test generation and passive testing techniques for conformance and robustness checking. The whole WebMov methodology is integrated within a dedicated framework, composed by a set of tools that implement the model representation, the test generation and passive testing algorithms. This framework also permits the interaction of these tools to achieve specific modelling and testing activities in a complementary way. A case study based on a real service, a Travel Reservation Web Service, is presented as well as the results of the application of the proposed WebMov methodology and tools.

Testing methodology for an ad hoc routing protocol

Ad hoc protocols, Testing, Verification, Model checking, PLTL, SPIN, Simulations. In this paper, we define a model of an ad hoc routing protocol, i.e. the OLSR (Optimized Link-State Routing) protocol. This model handles novel constraints related to such networks and issues new challenges to treat these constraints. In the network community, the practice is based on simulation models that allow to perform performance measures but no formal methods are used. We propose to promote the use of formal description techniques such as the promela and SDL languages that are both well accepted in the community of communication protocols. Until now, few works exist that handle the formal description of ad hoc networks, this network has as a main feature the absence of infrastructure. So, conformance testing and verification need to be revisited in order to bridge the gap between these new protocols and formal methods. In order to test and verify such protocols we need first to dispose of a formal model of what we want to verify and test. This is what we propose herein

Supple: a flexible probabilistic data dissemination protocol for wireless sensor networks

We propose a flexible proactive data dissemination approach for data gathering in self-organized Wireless Sensor Networks (WSN). Our protocol Supple, effectively distributes and stores monitored data in WSNs such that it can be later sent to or retrieved by a sink. Supple empowers sensors with the ability to make on the fly forwarding and data storing decisions and relies on flexible and self-organizing selection criteria, which can follow any predefined distribution law. Using formal analysis and simulation, we show that Supple is effective in selecting storing nodes that respect the predefined distribution criterion with low overhead and limited network knowledge.