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Consumer Driven Contracts �like TDD to the API

Olga Maciaszek-Sharma, @olga_maciaszek

Marcin Grzejszczak, @mgrzejszczak

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About us

Spring Cloud developer at Pivotal

Working mostly on

Spring Cloud Contract
Spring Cloud Netflix
Spring Cloud Gateway

Twitter: @olga_maciaszek

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About us

Spring Cloud developer at Pivotal

Working mostly on

Spring Cloud Sleuth
Spring Cloud Contract
CI / CD

Twitter: @mgrzejszczak

Blog: http://toomuchcoding.com

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Agenda

Introduction

Demo

Summary

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What we will NOT be talking about?

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Schema
WSDL
ESB
XSD
XSLT

What we will NOT be talking about?

THE IDEA OF SPRING CLOUD CONTRACT IS NOT TO INTRODUCE UNNECESSARY COUPLING OR REPLICATE OLD MISTAKES

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Producer

service that exposes an API / sends a message

Consumer

service that consumes the API of the producer / listens to a message from the producer

Contract

agreement between producer and consumer how the API / message will look like

Consumer Driven Contracts

approach where the consumer drives the changes of the API of the producer

Introduction

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What problems are we trying to solve?

Stub validity & reusability in the integration tests
Nice API creation

Introduction

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Typical situation

Introduction

HTTP

CONSUMER

PRODUCER

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How to write a test for it?

Introduction

HTTP

CONSUMER

PRODUCER

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How to write a test for it?

Introduction

HTTP

CONSUMER

PRODUCER

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WireMock

http://wiremock.org/

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A typical scenario

Introduction

WE’RE ON THE CONSUMER SIDE!!

CONSUMER OWNS THE STUB DEFINITIONS

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Stub validity & reusability

Introduction

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Let’s assume that we’re introducing a new endpoint...

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Introduction

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New endpoint

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Introduction

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So now what?

I write the missing code to work with the new URL
The unit and integration tests pass
Now we deploy to an environment �where real integrations take place...

Introduction

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Ooops...

Introduction

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What went wrong?

Stubs that were used in the build phase have nothing to do with the real API!!

Introduction

HTTP

CONSUMER

PRODUCER

TEST

OK

HTTP

CONSUMER

PRODUCER

REALITY

WAT?!

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Another example with messaging

Stubs that were used in the build phase have nothing to do with the real communication!!

Introduction

CONSUMER

PRODUCER

TEST

PRODUCER

CONSUMER

REALITY

topic: bar

topic: foo

topic: bar

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Stub validity & reusability - typical problems

Stubs reside with the consumer
Consumer controls the stubbing process
How are you sure that the stubs are valid?
What if other teams want to reuse those stubs?
How are you sure you’re listening to the proper topic / queue?
Are you sure you’ll deserialize your message properly?

Introduction

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Nice API creation

It’s the consumer that uses the API
Consumers should take part in the creation of the API of the producer
The producer’s API change should be driven by consumers

Introduction

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Nice API creation - no cooperation results

Introduction

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Nice API creation - no cooperation results

Introduction

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Potential answer

Spring Cloud Contract

Demo

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What are we going to code?

Consumer

service that gets beer requests
has to ask another service if the client can get the beer

Producer

service that checks if the client is old enough to buy beer

Feature

if the user is too young - the beer will not be sold
otherwise the beer will be granted

Demo

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What are we going to code?

Introduction

I’m 22 give me a beer

CONSUMER

PRODUCER

THERE YOU GO

Can the beer be sold?

status: OK, name: marcin

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What are we going to code?

Introduction

I’m 17 give me a beer

CONSUMER

PRODUCER

GET LOST

Can the beer be sold?

status: NOT_OK, name: marcin

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Who is who?

Demo

WHITE TERMINAL

WHITE IDE

CONSUMER

BLACK TERMINAL

BLACK IDE

PRODUCER

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Demo

Consumer’s offline work

Consumer Phase 1

Consumer Phase 2

Consumer’s switching to online

Producer phase

Producer’s implementing the feature

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Consumer flow 1

Demo

PRODUCER

CONSUMER CLONES PRODUCER

PRODUCER

CLONE

CONSUMER

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Consumer flow 1

Demo

PRODUCER

CONSUMER

CONSUMER CLONES PRODUCER

PRODUCER

CLONE

INTERACTION

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Consumer flow 1

Demo

PRODUCER

CONSUMER

PRODUCER

CLONE

INTERACTION

CONSUMER FILES �A PR

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Demo

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Producer flow

Demo

PRODUCER

TAKES OVER THE PR

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Producer flow

Demo

PRODUCER

TAKES OVER THE PR

WRITES THE MISSING IMPLEMENTATION

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Producer flow

Demo

PRODUCER

TAKES OVER THE PR

WRITES THE MISSING IMPLEMENTATION

MERGES TO MASTER

CI UPLOADS TO NEXUS / ARTIFACTORY

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Demo

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Consumer flow 2

Demo

CONSUMER

SWITCHES TO ONLINE MODE

DOWNLOADS STUBS OF COLLABORATORS DURING BUILD PHASE

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Demo

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I don’t want to write any scripts!

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Don’t worry! You can use �Spring Cloud Contract with YML

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Spring Cloud Contract with YML

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Spring Cloud Contract with YML

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If you must… then you can also use Swagger definitions

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Spring Cloud Contract with Swagger

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You can also use �Spring Cloud Contract with Rest Docs!!

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Spring Cloud Contract with Rest Docs

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With Spring Cloud Contract and Consumer Driven Contracts:

we’ve created an API that suits the consumer and the producer
expectations were defined by readable contracts
expectations were tested against the producer
producer stubs can be reused by consumers
starting and setting stubs is fully automated

Summary

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Learn More. Stay Connected.

Twitter: twitter.com/springcentral

YouTube: spring.io/video

LinkedIn: spring.io/linkedin

Google Plus: spring.io/gplus

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QUESTIONS

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