With the rapid development of Service-Oriented Architecture (SOA) and Service-Oriented Computing (SOC), the Quality of Service (QoS) is more and more essential than before. There are a number of tools and techniques for Web application testing, but few of these have addressed the procedure to gather user session data accessed in the production environment to assist testing SOA and SOC Web application performance, so as to apply appropriate user-level quality of service policy (user-level QoS) according to the test result. In this paper, we present a session-based user behavior meta-model (SUBM) to automatically generate test cases for user-level QoS load testing. SUBM represents realistic user behavior by exploiting user session information taken from server logs. The major contribution of this paper is the fundamental role of user behavioral authenticity in load testing. This paper also illustrates the prototype implementation of our session-based user behavior metamodel