RESHMI KRISHNA SENIOR CLOUD APPLICATION & PLATFORM ARCHITECT, PIVOTAL VINAY UPADHYA ADVISORY PLATFORM ARCHITECT, PIVOTAL TDD introduced many improvements into the development process with the biggest advantage relating to code design. As we move to a microservices based architecture, TDD becomes hard to implement across teams building different codebases. Consumer driven contracts (CDC) is like TDD but applied at the API level and is becoming more relevant in the world of microservices. It is a pattern for specifying and verifying interactions between different modules of an application. Spring Cloud Contract provides support for Consumer Driven Contracts and service schemas in Spring applications, covering a range of options for writing tests, publishing them as assets, asserting that a contract is kept by producers and consumers, for HTTP and message-based interactions. In this session, you will learn how we can implement TDD in microservices based architecture using Spring Cloud Contracts.

1. TDD for Microservices
By Reshmi Krishna By Vinay Upadhya
@reshmi9k @vinayu

2. About Us
Reshmi Krishna
● Software Engineer
● Platform Architect, Pivotal Cloud Foundry
● Women In Tech Community Member
Twitter : @reshmi9k
MeetUp : Cloud-Native-New-York
Vinay Upadhya
● Software Engineer
● Platform Architect, Pivotal Cloud Foundry
Twitter : @vinayu

3. Agenda
Testing Pyramid
What are Consumer Driven Contracts?
What problems are we trying to solve?
Spring Cloud Contract for microservices
Demo

4. Testing Pyramid
https://martinfowler.com/articles/microservice-testing/#conclusion-test-pyramid

5. What are Consumer Driven Contracts?
Internal
Marketing
App
External
Reseller
App
Product
Search
Service
A
P
I
{ catalogid, name,
price,
manufacturer }
{ catalogid,
name, price }
Product Schema
{ catalogid, name, price,
manufacturer,
inStock }
Producer
Contract
Expectation
Consumer
Contract
Consumer Driven
Contract

6. What does a contract look like?

7. What problems are we trying to solve?
1. Provide a framework for consumers to set
expectations using contracts with the
producer.
2. Have the producer own the stub generation
based on the consumer contracts to maintain
consistency.
3. Have the consumer build their application
confidently using TDD against the producer
validated stubs.
4. Producer test lifecycle includes validating
consumer contracts.
5. Minimize E2E integration tests.

8. Spring Cloud Contract
Spring Cloud Contract provides support for CDC and service schemas in Spring Apps.
Being part of Spring Cloud it can help stub out Spring Cloud components like Eureka,
Consul etc.
Comprised of three main projects :-
Spring Cloud Contract Verifier : Library on server side to test if the server isn’t breaking
any consumer contracts.
Spring Cloud Contract Wiremock : Wrapper around wiremock to help start stubs with
wiremock json stubs.
Spring Cloud Contract Stub Runner : Helper library to pull stubs from maven and run

9. Demo
I want to login
Can springdays/123 login ?
OK
OK
I want to login Can springdays1/123/123 login?
OKOK
Login Service

10. Demo
I want to login
Can Springdays/321 login?
NOT_OKAY
NO
I want to login Can springdays1/123/123as login?
NONOT_OKAY
Login Service

11. Typical CDC Flow
Consumer Phase 1 Producer Phase Consumer Phase 2
Consumer
Offline Work
Producer
Implementing
Feature
Consumer
Online Work

12. Consumer Flow 1 (Login Mobile Client)
Start TDD - writes the test for the feature
Write the missing implementation
Clone the Producer (LoginService) repository locally
Define the contract locally in the repo of Producer
Add the Spring Cloud Contract Verifier plugin
Run the integration tests

13. Producer Flow (Login Server)
Take over the PR
Write the missing implementation that will make the autogenerated tests pass
Merge PR and deploys the JARs with the app and the stubs

14. Consumer Flow 2 (Login Mobile Client)
Switches off the Stub Runner’s offline mode once the producer uploads the
stubs
Configure Stub Runner by providing the URL to a repo with stubs
Will have its test broken if the producer makes any breaking changes of the API

15. Resources
Docs : https://cloud.spring.io/spring-cloud-contract/spring-cloud-contract.html
MeetUp Demo : https://github.com/reshmik/spring-cloud-contract-login-demo.git
Consumer Driven Contracts (MarcinGrzejszczak) :
http://www.slideshare.net/MarcinGrzejszczak/consumer-driven-contracts-and-your-microservice-architecture-67641511
More Samples : https://github.com/spring-cloud/spring-cloud-contract/tree/1.0.x/samples
Talk to the SpringCloudContract Team : https://gitter.im/spring-cloud/spring-cloud-contract