Web Services (WS) is currently the major implementation of Service-Oriented Architecture (SOA). It defines a framework for agile and flexible integration among autonomous services based on Internet open standards. However, testing has been a challenge due the dynamic and collaborative nature of WS. This paper introduces an on-going project on a multi-agent based framework to coordinate distributed test agents to generate, plan, execute, monitor and communicate tests on WS. Test agents are classified into different roles which communicate through XML-based agent test protocols. Test Master accepts test cases from Test Generator, generates test plans and distributed them to various test groups. A set of test agents that implement a test plan are organized into a test group, which is coordinated by a Test Coordinator. Test Runners execute the test scripts, collect test results and forwards the results to Test Analyzer for quality and reliability analysis. The status of the test agents are monitored by the Test Monitor. Test agents are dynamically created, deployed and organized. Through the monitoring and coordinating mechanism, the agents can re-adjust the test plan and their behavior at run-time to be adaptive to the changing environment.