An enterprise service-oriented architecture is typically realized on a messaging infrastructure called an Enterprise Service Bus (ESB). An ESB is a bus which delivers messages from service requesters to service providers. Since it sits between the service requesters and providers, it is not appropriate to use any existing capacity planning methodology for servers, such as modeling, to estimate an ESB?s capacity. There are programs which run on an ESB called mediation modules. Their functionalities vary and depend on how people use the ESB. This creates difficulties for capacity planning and performance evaluation. This paper proposes a performance evaluation methodology and techniques for ESBs. We actually run the ESB on a real machine while providing a pseudo-environment around it. In order to ease setting up the environment we provide ultra-light service requestors and service providers for the ESB under test. We show that the proposed mock environment can be set up with practical hardware resources available at the time of hardware resource assessment. Our experimental results showed that the testing results with our mock environment are equivalent to the results in the real environment.