Load testing generally refers to the practice of modelling the expected usage of a software program by simulating multiple users accessing the program's services concurrently. As such, load testing is most relevant for a multi-user system, often one built using a client/server model, such as a web server. Sometimes, the load placed on the system is accelerated beyond normal usage patterns, in order to test the system's response at peak loads.
There is little agreement on what the specific goals of load testing are. The term is often used synonymously with performance testing, reliability testing, and volume testing.
Load testing is generally understood to stop short of stress testing, where the load is so great that error conditions are the expected result, though there is gray area in between.
See also software testing.