In software testing, stress testing refers to tests that determine the robustness of software by testing beyond the limits of normal operation. Stress testing is particularly important for “mission critical” software, but is used for all types of software. Stress tests commonly put a greater emphasis on robustness, availability, and error handling under a heavy load, than on what would be considered correct behavior under normal circumstances.


Reasons for stress testing include:

  • The software being tested is “mission critical”, that is, failure of the software (such as a crash) would have disastrous consequences.
  • The amount of time and resources dedicated to testing is usually not sufficient, with traditional testing methods, to test all of the situations in which the software will be used when it is released.
  • Even with sufficient time and resources for writing tests, it may not be possible to determine beforehand all of the different ways in which the software will be used. This is particularly true for operating systems and middleware, which will eventually be used by software that doesn’t even exist at the time of the testing.
  • Customers may use the software on computers that have significantly fewer computational resources (such as memory or disk space) than the computers used for testing.
  • Concurrency is particularly difficult to test with traditional testing methods. Stress testing may be necessary to find race conditions and deadlocks.
  • Software such as web servers that will be accessible over the Internet may be subject to denial of service attacks.
  • Under normal conditions, certain types of bugs, such as memory leaks, can be fairly benign and difficult to detect over the short periods of time in which testing is performed. However, these bugs can still be potentially serious. In a sense, stress testing for a relatively short period of time can be seen as simulating normal operation for a longer period of time.