A. Petrenko et al. (Eds.): TestCom/FATES 2007, LNCS 4581, pp. 13–27, 2007. © IFIP- International Federation for Information Processing 2007 New Approach for EFSM-Based Passive Testing of Web Services Abdelghani Benharref, Rachida Dssouli, Mohamed Adel Serhani, Abdeslam En-Nouaary, and Roch Glitho Concordia University 1455 de Maisonneuve West Bd, Montreal, Quebec H3G 1M8, Canada {abdel,m_serhan,ennouaar}@ece.concordia.ca, {dssouli,glitho}@ciise.concordia.ca Abstract. Fault management, including fault detection and location, is an important task in management of Web Services. Fault detection can be performed through testing, which can be active or passive. Based on passive observation of interactions between a Web Service and its client, a passive tester tries to detect possible misbehaviors in requests and/or responses. Passive observation is performed in two steps: passive homing and fault detection. In FSM-based observers, the homing consists of state recognition. However, it consists of state recognition and variables initialization in EFSM-based observers. In this paper, we present a novel approach to speed up homing of EFSM-based observers designed for observation of Web Services. Our approach is based on combining observed events and backward walks in the EFSM model to recognize states and appropriately initialize variables. We present different algorithms and illustrate the procedure through an example where faults would not be detected unless backward walks are considered. Keywords: EFSM-based passive testing, Web Services testing. 1 Introduction Web services, a rapidly emerging technology, offer a set of mechanisms for program- to-program interactions over the Internet [1]. Managing Web Services is critical because they are being actually used in a wide range of applications. Fault management including fault detection is an important issue in this management. Active testing and passive testing have been used for fault detection. An active tester applies test cases to the Web Service Under Test (WSUT) and checks its responses. In passive testing, messages received (requests) and sent (responses) by the Web Service Under Observation (WSUO) are observed, and the correct functioning is checked against the WSUT’s model. The observation is done by entities known as observers. Passive testing can complement active testing because it helps detecting faults that have not been detected before deployment. Furthermore, in many cases, it is a better alternative to active testing when the system is already deployed in its final operating