## 2 Related Works  
Although there exists many studies on protocol evaluation in WSNs, they mostly tackle their performance, application or security issues [12, 13]. Very few works focus on the conformance testing of these protocols. In the following, we present the ones that inspired us and compare them. In [21], the authors study common functional testing approaches to tackle the security issues in wireless sensor networks. Since conformance testing techniques cannot assess the efficiency of the implementation of a security protocol (mainly because most of the security concepts are close to non-functional mechanisms), the authors propose to add randomness tests to conformance tests dedicated to the evaluation of security functions. One part of the SPINS protocols (security protocols for sensor networks) is chosen to illustrate their approach. Like in the previous proposal, [22] recently proposed a remote testing method by stating the design and development of test routers in WSN. For that purpose, a remote testing platform is developed and assessed. The authors tackle the bad environment in which nodes are intensively placed. They study the energy consumption and the dynamic change of the network topology. These inherent constraints often prevent the testers from meeting the tested protocol requirements. Still, with the same objectives, a formal testing approach is proposed in [23]. A nodes' self-similarity approach for testing wireless mobile _ad hoc_ networks (MANET) is presented. Formal specifications and emulations are applied through the Dynamic Source Routing (DSR) [24] protocol to provide relevant verdicts about the test of one of its implementations. We also got inspiration by [25] in which real wireless sensor nodes are deployed to test, through virtualized emulated nodes, TCP and some functions of their own faulty routing protocol RMRP (Rime mesh routing protocol). A state model is defined and test suites generated and executed through their architecture based on an interesting generated dynamic topology. In recent papers [26, 27], the authors provided a suitable open conformance test system for standard-based WSNs, dedicated to the protocol evolution and the various hardware interfaces of the sensor nodes. However, these approaches do not provide a way of modeling non-standardized requirements as we tackle in this work. In our work, we propose an approach to test the functional behaviors without using any formal specifications. Further, we do not claim to interact with the designers through any testing process, but just by receiving the expected protocol requirements. Though interesting results have been obtained by the works mentioned above, the tests are mostly applied through active testing architectures. The tests are intrusive and need to generate important test suites. One of our challenges is to the contrary to avoid any interaction with the implementation. By passively testing the implementation protocols, we also do not need any testing scripts and the related specification stages. Moreover, we here work on a real testbed, avoiding the simulation or emulation drawbacks often met in these kind of studies. Recently, interesting works on passive diagnostics in WSN have been presented. First, we may cite [28] in which the authors propose a probabilistic diagnosis approach for inferring the root causes model of abnormal phenomena in wireless sensor networks through the passive observation of eventual symptoms. A light-weight packet-marking scheme is defined to collect relevant hints and the probabilistic inference model located at the sinks targets the expected hints. Second, [29] proposes a passive observation and mining of relevant collected information to diagnose WSN performance failures. The authors' technique deduces the root causes of failures by focusing on the relationships between the sensing data, the failures in the networks and a failure knowledge library. Furthermore, [30] proposes passive distributed assertions (PDA) as a novel tool for identifying failure causes.