API Contract Test Cross Service Workflow
Implement cross-service contract testing to verify that service integrations remain compatible during independent deployments.
Objective
Prevent integration failures with automated contract testing between services.
Environment
- Multiple services with API dependencies
- A contract testing framework
- CI pipelines for each service
Steps
1. Define contracts
For each consumer-provider pair, define the expected request and response contracts.
Expected state: Contracts are defined for all service integrations.
2. Implement consumer tests
Write consumer tests that generate pact files from the consumer expectations.
Expected state: Consumer tests generate pact files.
3. Set up provider verification
Configure provider CI to verify pacts against the provider implementation.
Expected state: Provider CI verifies contracts on every change.
4. Use a pact broker
Publish pacts to a broker so providers can fetch and verify the latest consumer expectations.
Expected state: Pacts are published and verified through a broker.
5. Test the pipeline
Make a breaking change to a provider and verify the contract test catches it.
Expected state: Contract tests catch breaking changes before deployment.
Decision points
Pact or OpenAPI-based?
- Pact for consumer-driven
- OpenAPI for provider-first
Use Pact for consumer-driven contracts; OpenAPI for provider-first with generated stubs.
Expected outcome
Cross-service contract testing is implemented and catches breaking changes in CI.
Verification
Make a breaking API change and confirm the contract test fails in CI; revert the change and confirm tests pass.
Cleanup
Remove test pacts after verification; keep the contract testing infrastructure active.
Contracts prevent integration drift
When services deploy independently, contract tests ensure they still work together without full integration tests.
Implementation Notes
This workflow provides a structured approach to ensure consistent results across team members and environments.
Common Pitfalls
Skipping verification steps or rushing through the process can lead to incomplete results. Always follow each step in order and verify before proceeding.
Quick Reference
# Execute the workflow steps as documented above
echo "Workflow completed successfully"