A counterexample is a concrete case that tests a business rule by showing where an expected behavior does not apply. Teams use counterexamples during collaborative requirements conversations to expose hidden assumptions, clarify acceptance criteria, and build shared understanding. section 6.0 section 1.1
Use counterexamples to challenge an apparently obvious rule:
- Ask “What if...?”, “Is this always the case?”, or “Are there examples where this rule does not apply?” section 6.4.2
- Record the case beside ordinary examples so the boundary of the rule becomes explicit. section 6.3
- Turn the clarified examples into business-readable acceptance criteria and, where appropriate, automated acceptance tests. section 1.1
Previous-flight eligibility
A rule says that flights within 90 days of sign-up qualify for credit. A flight 100 days ago is a counterexample because it is too old. Further counterexamples reveal that a partner flight, a cancelled flight, and a future confirmed flight are also ineligible, even when other conditions appear to fit. section 6.3
Compare eligible and ineligible flights by number, date, status, and reason to see how counterexamples refine a rule. section 6.3
