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.{{cite web|url=http://glossary.istqb.org/search/test%20object|title=ISTQB Glossary|website=glossary.istqb.org|accessdate=2018-02-05}}{{cite web|url=https://robots.thoughtbot.com/don-t-stub-the-system-under-test|title=Don't Stub the System Under Test|website=robots.thoughtbot.com|date=22 November 2013 |accessdate=2018-02-05}}{{cite web|url=https://www.itwissen.info/SUT-system-under-test.html|title=SUT (system under test)|website=www.itwissen.info|language=de|accessdate=2021-02-24}}

From a unit testing perspective, the system under test represents all of the classes in a test that are not predefined pieces of code like stubs or even mocks. Each one of this can have its own configuration (a name and a version), making it scalable for a series of tests to get more and more precise, according to the quantity of quality of the system in test.