In this work, we develop a hierarchical load testing architecture using large scale virtual clients to reduce the testing time and ensure the stability of the server for distributed applications. It explicitly secures the stability of the servers for networked virtual environment and at the same time, it elaborately generates actual loads for testing the performance of the servers. Our agent based load testing architecture provides variety of interactions of virtual entities in the virtual worlds to perform realistic simulations. Simulation results illustrate that our proposed architecture ensures the stability and capacity of the servers for both massively multiplayer online games and peer-to-peer network games.