hardConceptScenarioDesignMidSeniorStaff
Your consumer-driven contract test passes in CI, but production rejects a request because a supposedly optional field is missing. What did the contract testing actually miss?
The contract captured the shape the consumer sends, not the rules the provider enforces. Optionality lived in the schema while the real requirement lived in provider validation, and no recorded example ever omitted the field. Contract tests only verify interactions they contain, so add the negative example and verify against real code.
4 min readUpdated 2026-08-16Target archetype: Big Tech, Enterprise Captive, Product Startup
Answer
Short answer
A contract test verifies the interactions it contains and nothing else. If the consumer's contract never included an example that omits the field, no test ever asked the provider what happens when it is absent — so "optional" was an assumption written into a schema, never a behaviour anyone verified. The provider's validation says otherwise, and production is the first place the two met.
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Likely follow-ups
- Where exactly would you add a test, and what would it assert?
- The provider verification runs against a stubbed service layer. What does that invalidate?
- How does a broker with can-i-deploy change this outcome?
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- When is contract testing the wrong tool and you should just run an integration test?
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