The document discusses microservices testing, particularly emphasizing consumer-driven contracts (CDC) using the Pact framework to enhance testing efficiency and reliability. It outlines the challenges with various testing types (component, integration, and end-to-end tests) and presents CDC as a solution to reduce feedback loops while ensuring service compatibility. Additionally, it covers Pact's capabilities for tagging application versions and maintaining a compatibility matrix, ultimately helping teams decide on deployment and release strategies.

1. Microservices testing:
Consumer driven
contracts using Pact
By Paresh Mahajan & Prashant Kalkar

2. Essence of Testing

3. Reducing the feedback loop
How can we shorten the loop?
● Automation
● Scheduled builds - Continuous Integration
● Test segregation
Larger the loop more costly it is.

4. Build Pipeline

5. Test pyramid

6. Testing challenges in Microservices
● Revisiting the testing terms
● Do we need any other types of test?
● Does the system works end-to-end?

7. Test pyramid in case of Microservices

8. Component Tests
Tests a single service as black box. External services are stubbed.

9. Challenges in Component Tests

10. Integration tests

11. Issues with Integration tests
● Difficult to setup due to service dependency graph
● Can quickly increase in numbers for large number of services
● If setup incorrectly can be brittle to maintain
● Some stubs can be used but integration with real service still needs to be
covered in some other tests
● Stubs needs to be kept up to date to keep these tests relevant/useful

12. End to End tests

13. Issues with E2E tests
● Slow feedback
● Test data setup difficult
● Brittle, non-deterministic tests
● Harder to debug the test failure
● Parallel execution difficult to achieve
● No good way of scheduling them

14. Is there any golden mean which will allow us faster
execution as well as will give us more confidence if the
system works as a whole?

15. Consumer Driven Contracts

16. Consumer Driven Contracts (CDC)
● A CDC framework allow us to use the stub during component tests but also
provide a way to ensure that the service will work with actual services.

17. How CDC framework works:
Contract / Pact
stored between
Consumer & Producer
Contract/Pact
Executed Against

18. Example in Discussion
Consumer Provider

19. Consumer Test (Order Service)

20. Provider Test (User Service)

21. Demo
● Order service tests
● User service tests

22. CDC benefits
● Consumer component tests can be reused for CDC
● Solves the issues of stale stubs
● Provides end to end test benefits without extra cost
● Faster Feedback
● Can be part of Consumer and Producer (independent) pipelines
● Producer can be tested againsts all the Consumers

23. Avoid Pitfalls

24. Beware of Contract Coupling
● Contracts only contains fields required by Consumer. (It may not be same
as Producer’s entire response)
● When tested against producer extra fields in response are ignored
● Leads to loose coupling between consumers and producers
● Pact CDC framework implements Postel’s law while doing Pact verification

25. Releasability

26. What We Test Vs What We Release Monolith

27. What we Test Vs What We Release -
Microservices

28. Compatibility
CDC testing between latest services is not sufficient.
How to answer ‘Can I deploy/release this service in Production?’

29. Pact tagging
● Pact allows us to tag application versions.
● An application/service version can be tagged as say DEV or PROD.
● Pact broker maintains a compatibility matrix between applications.

30. Pact Matrix

31. Producer and Releasability
Latest
Dev
Prod
TAGS
2. Execute all pacts against the Producer

32. Consumer and
Releasability

33. 1. Run tests
2. New Pacts published
3. Triggered by Webhook

34. Releasability and Pipeline Demo
● Consumer pipeline
● Provider pipeline
● Non compatible change in Provider
● Deploy Provider and Consumer till production
● Non compatible changes in consumer
● Provider fix as per new consumer contract
● Deploy new Provider to DEV
● Deploy new Consumer to DEV (can-i-deploy pass)
● Deploy new Consumer to PROD (can-i-deploy fail)
● Consumer changes (Pre-verified Contracts)

35. Thank you!
Git repositories:
https://github.com/prashant-ee/cdc-pact-expert-talk/
https://github.com/prashant-ee/user-service
https://github.com/prashant-ee/order-service