Cause-effect Graph
A cause-effect graph is a black-box test design technique that models logical relationships between inputs and outputs to derive effective test cases.
“A graphical representation of logical relationships between inputs (causes) and their associated outputs (effects) of a test object.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Cause-effect Graph?
Cause-effect graphs represent combinations of input conditions (causes) and resulting system actions (effects). They help testers design tests for complex business rules.
Logical relationships: Inputs and outputs are connected using Boolean logic.
Test design: The graph is converted into test cases, often using decision tables.
Benefit: Reduces missed combinations in complex logic.
Real World Example
A regulated product team is preparing a release where Cause-effect graph appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Cause-effect graph 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 Cause-effect graph and similar ideas.
The page becomes useful in practice because Cause-effect graph is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which BEST describes cause–effect graph use in testing?
Question 2
Why choose a cause–effect graph?
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