Testing and verification methodologies for wireless sensor networks (WSN) systems in pre-deployment are vital for a successful deployment. Increased visibility of the internal state of a WSN application is established by instrumenting the application for logging execution traces at runtime. While the interpretation of the event traces is application-specific, a common method for analysis can be devised. This method should allow for a concise formulation of explorative queries to determine the occurrence and the cause of functional or performance problems. The contribution of this paper is an event analysis methodology that is implemented in the EvAnT framework. EvAnT allows for specifying queries that are executed on the collected traces. EvAnT is specifically tailored to WSN testing and debugging. We demonstrate the applicability of EvAnT by a case study in a building monitoring project.