Contract testing involves a suite of tests that validate the API contracts between services, ensuring that both consumer and provider uphold these agreements during development and deployment. The use of contract tests promotes resiliency in production, prevents potential breaks from API changes, and serves as documentation for the API. Fakes are locally developed by consumer teams and allow for testing against a minimal implementation of the production provider, facilitating integration within continuous integration pipelines.

1. Contract Testing
An Introduction

2. What are they?
A suite of tests that allow you to “work with mocks that represent the
agreed-upon API contract between the services, but also, the
services (or teams really) that provide the API for consumption have
to uphold that API contract that is used in those mocks, and the
contract is enforced in their CI so they can’t break the API and go to
production.”
https://bit.ly/36Y6jMe

3. Why use Contract Tests?
• Work with mocks
• Be sure that the mocks represent the production API
• Help with resiliency when deploying to production
• Help ensure changes to APIs do not break in production
• Provide early warning to possible breaks
• Provide documentation for an API
• Provide mutually understandable code

4. https://bit.ly/36Y6jMe

5. Code Example (Java)

6. Fakes
• Developed locally by the Consumer team
• Represent a minimum viable implementation of the production
Provider
• Allow the tests against the Consumer to run locally
• Provide certainty that the code will work in production
• Can be easily integrated into a continuous integration pipeline

7. ProviderConsumer
Fake
Provider
Using Fakes
Service
Test
Contract
Test

8. Thanks