Stick to the rules - Consumer Driven Contracts. 2015.07 Confitura

Stick to the rules!Consumer Driven Contracts

04.07.2015 - Confitura PL

Marcin Grzejszczak @mgrzejszczak

@confiturapl @mgrzejszczak / @4financeit

Swim for a dreamhttp://swimforadream.com/Adam will swim 18.5 km from Hel to GdyniaMoney for 3 charity organizations

http://swimforadream.com/

http://swimforadream.com/


Marcin Grzejszczak● Software Architect at 4financeIT● Author of "Mockito Instant", "Mockito Cookbook"● Co-author of "micro-infra-spring",

“spring-cloud-zookeeper”, “spring-cloud-sleuth”

Twitter: @MGrzejszczakBlog: http://toomuchcoding.blogspot.comHomepage: http://marcin.grzejszczak.pl


Agenda

● Short introduction● Real life scenario with a hilarious joke● How does it work?● Live (hopefully) coding● Summary


Consumer Driven Contracts

● TDD on architectural level○ mistakes occur both in implementation and design

● Try to use API before implementing it


Real life scenario...



Hi! I’m team X and we have spent weeks to tweak our code to use your API!



That’s so sweet… But we’ve just changed our API because well, it’s ours.



You’ve got to be shitting me! (however it sounds)




CDC building blocks

● Server● Consumer● Contract


CDC building blocks


How to make life easier?

Use common contract


Contract definition


What is a contract?io.codearte.accurest.dsl.GroovyDsl.make { request { method "PUT" url "/fraudcheck" body(''' { “clientPesel":"12345678901", "loanAmount":123.123 } ''' ) headers { header("Content-Type", "application/fraud+json") } } response { status 200 body( """{ "fraudCheckStatus": "OK"}""") headers { header('Content-Type': 'application/fraud+json') } }}



Groovy DSL



FOR A GIVEN REQUEST



WE’LL HAVE SUCH A RESPONSE


So how am I supposed to work?


Workflow - Consumer side

CLONE SERVER REPO AND WORK OFFLINE



1) ALTER THE CONTRACT LOCALLY2) GENERATE AND COPY STUBS3) USE STUBS IN CONSUMER TESTS


What is a stub?

● JSON representation of a Groovy DSL contract

● Understood by Wiremock Http Server Stub



FILE A PULL REQUEST WITH THE PROPOSED CONTRACT


Server tests - what happens there?

● server has DSLs with contracts

● tests are generated from the contracts

● stubs that consumers can use are generated from the contracts


Workflow - Server side

● oh, I have a PR with the proposed contract

● I don’t have the implementation ready so my generated tests are failing

● I’ll add the implementation, fix the tests and merge the PR!


Workflow - Server side

IMPLEMENTATION IS READYI’LL PUBLISH MY STUB!


Consumer TechnologyWiremock

http://wiremock.orgtestCompile 'com.github.tomakehurst:wiremock:1.56'

{ "request": { "method": "GET", "url": "/hello" }, "response": { "status": 200, "body": "Hello world!", "headers": { "Content-Type": "text/plain" } }}

Configuration

Sample definition

http://wiremock.org

http://wiremock.org


Server TechnologyAccurate REST

https://github.com/Codearte/accurest

buildscript { repositories { mavenCentral() } dependencies { classpath 'io.codearte.accurest:accurest-gradle-plugin:0.7.0' }}

apply plugin: 'accurest'




Example


New feature


Let consumer drive the contract!


Live coding - consumer side


Consumer prepared the contractio.codearte.accurest.dsl.GroovyDsl.make { request { method "PUT" url "/fraudcheck" body(''' { “clientPesel":"1234567890", "loanAmount":99999 } ''' ) headers { header("Content-Type", "application/vnd.fraud.v1+json") } } response { status 200 body( """{ "fraudCheckStatus": "REJECTED", "rejectionReason": "Amount too high" }""") headers { header('Content-Type': 'application/vnd.fraud.v1+json') } }}


Time for server side implementation!


Live coding - server side


CDC benefits


CDC benefits

● Rapid API prototyping

● Non-blocking development

● Behaviour Driven Development


CDC benefits

● Client tells what he needs

● Quality - continuously checking if contract is valid


CDC benefits

● if server breaks API compatibility consumer tests fail

● if server adds new API I can reuse it immediately in my tests


CDC benefits

● The server tests are generated for you

● Any typos / misunderstandings will be found out immediately


Not so fast...● Maintaining datasets● What exactly to verify for server side?● Breaking changes● Accurest under development

○ I also have to sleep sometimes


Q&Ahttps://github.com/marcingrzejszczak/2015_confitura_cdc

Accurest: https://github.com/Codearte/accurestMicro-Infra-Spring: https://github.com/4finance/micro-infra-springCDC: http://martinfowler.com/articles/consumerDrivenContracts.html

https://github.com/marcingrzejszczak/2015_confitura_cdc

https://github.com/marcingrzejszczak/2015_confitura_cdc


https://github.com/4finance/micro-infra-spring

http://martinfowler.com/articles/consumerDrivenContracts.html

Stick to the rules - Consumer Driven Contracts. 2015.07 Confitura

Documents

financeit swim

mgrzejszczak blog

financeit real life

financeit contract definition

applicationfraud json

url fraudcheck body

life easier

common contract