Web services are pieces of software offering functionalities to other (remote) machines over the Internet that work based on the Service-Oriented Architecture (SOA). They can be invoked by means of Web related standards (usually, SOAP, UDDI, XML, HTTP, WSDL. In the recent years, the usage of Web services has increased due to the flexibility and interoperability among heterogeneous platforms and operative systems that they provide. SOA adds value in terms of low coupling, re-usability of services and sharing; it makes the systems flexible and adaptive in case of changes in the business process and improves the integration of heterogeneous systems. Besides, new ways of using Web services have emerged, by combining them in order to create more complete (and complex) services. This process of re-using and combining Web services is called Web service composition, and its main objective is to allow the re-usability of the functionalities proposed by the Web services. This is why this architecture has been widely accepted by the companies all over the world: it helps reducing the cost and time to create business processes, and this is the type of systems we work with in this thesis, more specifically, we aim at ensuring their correct behavior by using testing techniques in order to detect possible errors.

Les services Web sont des logiciels qui offrent des fonctionnalités à des autres machines à travers l'Interent. Les services Web sont basés sur l'Architecture Orientée Services (SOA, pour son nom en anglais). Ils peuvent être invoqués en utilisant des standards pour le Web (normalement, SOAP, UDDI, XML, HTTP, WSDL). Dan les dernières années, l'utilisation des services Web s'est incrémentée à cause de la flexibilité qu'ils offrent, ainsi comme de l’intégration des systèmes hétérogènes. En plus, SOA ajoute de la valeur dans le sens où les services peuvent être réutilisés et partagés; cela fait les systèmes plus flexibles et adaptables en cas où il y a des changements dans les processus de l’entreprise, et améliore l'intégration des systèmes. Aussi, des nouvelles façons d'utiliser les services Web se sont développées, en combinant pour créer des services plus complets et complexes. Le processus de réutiliser les services Web pour créer des nouveaux s'appelle composition des services Web, et son but principal est de permettre la réutilisation des fonctionnalités proposées par les services Web. C'est pour cette raison que l'architecture SOA a été bien acceptée par les entreprises partout dans le monde: elle aide à réduire le coût et le temps qu'il faut pour créer des solutions, et c'est la composition des services Web qu'on étudie dans cette thèse. Plus spécifiquement, on veut assurer leur correct comportement en utilisant des techniques du test pour détecter des possibles erreurs. / Web services are pieces of software offering functionalities to other (remote) machines over the Internet that work based on the Service-Oriented Architecture (SOA). They can be invoked by means of Web related standards (usually, SOAP, UDDI, XML, HTTP, WSDL. In the recent years, the usage of Web services has increased due to the flexibility and interoperability among heterogeneous platforms and operative systems that they provide. SOA adds value in terms of low coupling, re-usability of services and sharing; it makes the systems flexible and adaptive in case of changes in the business process and improves the integration of heterogeneous systems. Besides, new ways of using Web services have emerged, by combining them in order to create more complete (and complex) services. This process of re-using and combining Web services is called Web service composition, and its main objective is to allow the re-usability of the functionalities proposed by the Web services. This is why this architecture has been widely accepted by the companies all over the world: it helps reducing the cost and time to create business processes, and this is the type of systems we work with in this thesis, more specifically, we aim at ensuring their correct behavior by using testing techniques in order to detect possible errors.