How does a client/server environment affect testing?

Client/server applications can be quite complex due to the multiple dependencies among clients, data communications, hardware, and servers, especially in multi-tier systems. Thus testing requirements can be extensive. When time is limited (as it usually is) the focus should be on integration and system testing. Additionally, load/stress/performance testing may be useful in determining client/server application limitations and capabilities. There are commercial tools to assist with such testing.