Test Double
A test double is a generic term for an object or component that replaces a real dependency during testing.
“A replacement component invoked by a test object to perform testing.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Test Double?
Test doubles include stubs, mocks, fakes, spies, and dummies, allowing components to be tested in isolation from external dependencies.
Dependency replacement: Simulates unavailable or unnecessary components.
Isolation: Focuses testing on the component under test.
Multiple types: Includes mocks, stubs, fakes, spies, and dummies.
Real World Example
A regulated product team is preparing a release where Test double appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Test double 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 Test double and similar ideas.
The page becomes useful in practice because Test double is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which statement BEST describes Test double in the context of ISTQB terminology?
Question 2
A tester needs to explain Test double to a non‑technical stakeholder. Which approach is MOST appropriate?
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