Moez Krichen

Automated Significant Load Testing for WS-BPEL Compositions

Web service compositions must provide services to hundreds even thousands of users concurrently. These applications must be load tested to ensure that they can function properly under high load. We propose in this paper a solution for load testing of WS-BPEL compositions. It is based on Timed Automata as model for specifying requirements to test under various load conditions, a distributed testing architecture, an algorithm for online load test generation and execution, and finally an automated log analysis technique. We also illustrate our approach by means of a case study.

Towards a TTCN-3 Test System for Runtime Testing of Adaptable and Distributed Systems

Today, adaptable and distributed component based systems need to be checked and validated in order to ensure their correctness and trustworthiness when dynamic changes occur. Traditional testing techniques can not be used since they are applied during the development phase. Therefore, runtime testing is emerging as a novel solution for the validation of highly dynamic systems at runtime. In this paper, we illustrate how a platform independent test system based on the TTCN-3 standard can be used to execute runtime tests. The proposed test system is called TT4RT: TTCN-3 test system for Runtime Testing. A case study in the telemedicine field is used as an illustration to show the relevance of the proposed test system.

Model-Based Conformance Testing of WS-BPEL Compositions

We propose in this paper a new approach for conformance testing of WS-BPEL compositions. It is based on Timed Automata as model for testing WS-BPEL implementations, a distributed testing architecture and an algorithm for online test generation and execution. We also implemented our solution in the form of a prototype tool named WSCCT.

Using Knapsack Problem Model to Design a Resource Aware Test Architecture for Adaptable and Distributed Systems

This work focuses on testing the consistency of distributed and adaptable systems. In this context, Runtime Testing which is carried out on the final execution environment is emerging as a new solution for quality assurance and validation of these systems. This activity can be costly and resource consuming especially when execution environment is shared between the software system and the test system. To overcome this challenging problem, we propose a new approach to design a resource aware test architecture. We consider the best usage of available resources (such as CPU load, memory, battery level, etc.) in the execution nodes while assigning the test components to them. Hence, this work describes basically a method for test component placement in the execution environment based on an existing model called Multiple Multidimensional Knapsack Problem. A tool based on the constraint programming Choco library has been also implemented.

Study on the Limitations of WS-BPEL Compositions Under Load Conditions

Web services compositions are still considered as a major player in the implementation of distributed architectures. Such applications must provide services to hundreds of users simultaneously. In this context, load testing of these applications seems an important task in order to detect problems under elevated loads. For this purpose, we proposed a distributed test architecture aiming to study the behavior of WS-BPEL compositions considering load conditions. The developed test approach is performed based on two steps. The first one is to run a load test during which the composition under test is monitored and performance data are recorded. The second step is to analyze the resulting test logs in order to identify problems under load. For that, we proposed a classification of these problems according to both their natures and causes. Finally, we concretized our solution by implementing a testing tool (WSCLim) and we evaluated it in the context of a Travel Agency case study.

Conformance testing for quality assurance of clustering architectures

Given the scalability of load balancing based architectures, it is increasingly necessary to develop appropriate quality assurance methodologies and techniques, of which Testing is widely adopted and used one. This paper describes a distributed platform for checking the conformance between real functioning of a given load balancer and its specified requirements. Our solution is based on Timed Automata as model for testing supported load balancing algorithms. This paper also shows a novel prototype tool support, LBACT, implemented for quality assurance of load balancing based architectures. Finally, we illustrate our contribution in the context of BPEL clustering mechanisms.

A formal framework for black-box conformance testing of distributed real-time systems

We extend our previous work on model-based conformance testing (Bensalem et al., 2007; Krichen and Tripakis, 2009). We propose a formal framework for black-box conformance testing for distributed real-time systems. Our framework is based on the model of partially-observable, non-deterministic timed automata. A given distributed system can be modelled either as a single timed automaton or a network of timed automata. We recall the definition of the timed input-output conformance relation tioco. We consider two types of tests: analogue-clock tests and digital-clock tests. Our algorithm for generating analogue-clock tests is based on an on-the-fly determinisation of the specification automaton during the execution of the test, which in turn relies on reachability computations. We also provide algorithms for static or on-the-fly generation of digital-clock tests. These tests measure time only with finite-precision digital clocks. Our testing architecture may be either centralised or not.

Test Isolation Policy for Safe Runtime Validation of Evolvable Software Systems

Runtime testing of dynamically evolvable systems is known as a complex and challenging activity. Undesired side effects may be introduced as the interference between test cases and business functionalities of the components under test. To handle such problem, test isolation strategies are used to execute runtime tests safely. In this proposal, we discuss the need to adapt the well known test isolation mechanisms to cope with heterogeneity of the components under test. For doing this, we define a Test Isolation Policy that produces the suitable test isolation solution depending on the testability degree of each component under test. We show its usefulness by the means of a case study in the healthcare domain, called Teleservices and Remote Medical Care System (TRMCS). Some experiments are carried out to show the efficiency of our approach and the low overhead it introduces.

WSCCT: a tool for WS-BPEL compositions conformance testing

WS-BPEL is considered as the emerging standard for Web service compositions. As more and more compositions are modeled using WS-BPEL, ensuring good quality of WS-BPEL codes becomes crucial. This paper shows a novel tool, WSCCT, implemented for conformance testing of WS-BPEL compositions. It is based on Timed Automata as model for online testing of WS-BPEL implementations. The tool is being extended with graphical user interfaces. Besides, we illustrate how to use our proposed tool for conformance testing of a travel agency scenario which is implemented in BPEL.

Runtime testing framework for improving quality in dynamic service-based systems

Service-based systems are operating in dynamic environments characterized by continual changes such as requirement evolution, service crash or service unavailability. In this context, improving the quality of these systems after such evolution is highly demanded. With the aim of checking their behaviors at runtime and detecting faults introduced after dynamic changes, a runtime testing approach is applied. An effective Runtime Testing Framework For Adaptable and Distributed Systems called RTF4ADS is then proposed. This framework is conceived in order to reduce runtime testing side effects as timing and resource usage costs, interference risks while improving its fault finding capabilities. To show the relevance of RTF4ADS prototype, a case study in the healthcare domain implemented in the OSGi platform is given.