Stress testing is a form of testing which is used to determine the stability of a given system or entity. It involves testing beyond normal operational capacity, often to a breaking point, in order to observe the results. For example, a web server may be stress tested using scripts, bots, and various denial of service tools to observe the performance of a web site during peak loads. Stress testing a subset of load testing. Also see testing, software testing, performance testing.

Medical context: Cardiac stress test is used mostly commonly to identify problems with blood flow to the heart muscle, sometimes other issues.