Implement consumer-driven contract testing for API boundaries

Integration tests that require both services running at the same time are slow, brittle, and hard to maintain. Consumer-driven contract testing decouples the consumer and provider test suites — each team can run their tests independently, yet the broker guarantees that the published contract is always verified against the live provider. This catches API mismatches days earlier than end-to-end tests, with far less infrastructure overhead.

Quick Reference

• The consumer writes tests that describe what it expects from the API (the "contract")
• The contract is published to a Pact Broker and verified against the real provider
• Provider changes that break the contract fail CI before they are deployed
• This replaces fragile end-to-end tests that require both services to be running simultaneously

Check

Check whether the frontend has consumer-driven contract tests that define and verify the API contract with the backend.

Fix

Add Pact consumer tests for the frontend API client, publish the contracts to a broker, and add provider verification to the backend CI pipeline.