System under test

System under test (SUT) refers to a system that is being tested for correct operation. According to ISTQB it is the test object.

From a unit testing perspective, the system under test represents all of the classes in a test that are not predefined pieces of code such as stubs or mocks. Each class under test can have its own configuration, such as a name and version, allowing test suites to scale as the system's complexity grows.

ISO/IEC/IEEE 29119 defines SUT within a standardized vocabulary and test-process framework.

See also

References

  1. ↑ "ISTQB Glossary". glossary.istqb.org. Retrieved 2018-02-05.
  2. ↑ "Don't Stub the System Under Test". robots.thoughtbot.com. 22 November 2013. Retrieved 2018-02-05.
  3. ↑ "SUT (system under test)". www.itwissen.info (in German). Retrieved 2021-02-24.
  4. ↑ "ISO/IEC/IEEE 29119-1:2022 — Software testing — Part 1: Concepts and definitions" (PDF). ISO/IEC/IEEE. 2022. Retrieved 17 September 2025.