System Under Test
The system under test (SUT) is the software system, application, or component that is being evaluated during testing.
“A type of test object that is a system.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is System Under Test?
The SUT is the primary object of testing, while supporting tools, environments, and test doubles interact with it during execution.
Testing target: The SUT is the focus of all test activities.
Scope definition: Clearly identifies what is being tested.
Isolation: External dependencies may be simulated or controlled.
Real World Example
A regulated product team is preparing a release where System under test appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats System under test as interchangeable with nearby ISTQB terms. That makes test scope blurry and can lead to weak evidence for the release decision.
The tester anchors the discussion in the official definition, asks where the concept appears in the product, and designs examples that show the difference between System under test and similar ideas.
The page becomes useful in practice because System under test is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which statement BEST describes System under test in the context of ISTQB terminology?
Question 2
A tester needs to explain System under test to a non‑technical stakeholder. Which approach is MOST appropriate?
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