Assertion
An assertion is a statement embedded in software that checks whether a specified condition is true during program execution.
“A Boolean expression that is expected to evaluate to true if and only if the software executes correctly.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Assertion?
Assertions help developers detect programming errors early by automatically verifying assumptions about program state while the software is running.
Development aid: Assertions identify incorrect assumptions during coding and testing.
Failure indication: An assertion failure usually signals a programming defect.
Testing value: Assertion failures provide useful diagnostic information during debugging.
Real World Example
A regulated product team is preparing a release where Assertion appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Assertion 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 Assertion and similar ideas.
The page becomes useful in practice because Assertion is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which statement BEST describes an assertion in unit testing?
Question 2
Which practice MOST improves assertion quality?
Test your knowledge with real ISTQB-style questions
You’ve learned Assertion. Test your understanding with topic-specific questions in our Mock Exams.