Contract test serverless integrations before production

Serverless integrations often fail at the boundary: a producer changes an event field, an API response loses a required value, or an authorization rule shifts without the consumer noticing. Unit tests inside each service cannot reliably catch those changes.

Test the agreed shape

Keep a versioned example or schema for each published API and event. Test that the producer emits it and that the consumer can handle the compatible forms it claims to support. Include failure cases, optional fields, authorization outcomes, and representative payload sizes.

Run these tests in the delivery path before a contract reaches production. For AWS integrations, add a small environment test where service policies, event source mappings, and serialization behave as they do in the account.

Contract tests are not a replacement for end-to-end testing. They make the ownership boundary explicit so an integration can evolve deliberately.