Marcin Grzejszczak, Jakub Kubryński Language: English Stick to the rules! Consumer Driven Contracts as a TDD on architectural level TDD introduced many improvements into development process, but in our opinion the biggest impact relates to code design. Looking at the code from the usage perspective (by first writing an acceptance test) allows us to focus on usability rather than concrete implementation. Unfortunately usually we rest on laurels not trying to uplift this practice into architecture level. Consumer driven contracts are like TDD applied to API. It’s especially important in the world of RESTful endpoints and microservices. Since it’s driven by consumers it’s much more user friendly. Of course microservices are really cool, but most people do not take into consideration plenty of potential obstacles that should be tackled. Then instead of frequent, fully automated deploys via delivery pipeline, you might end up in an asylum due to frequent mental breakdowns caused by production disasters. In this talk we will try to show you how to write tests of your microservice's contracts so that your chances to go down on production due to sending improper requests get lowered substantially. We’ll present how to move TDD to the architecture level and design the API from the consumer’s point of view.

1. Stick to the rules!
Consumer Driven Contracts
Marcin Grzejszczak @mgrzejszczak
Jakub Kubrynski @jkubrynski

2. Jakub
Kubryński
@jkubrynski
www.kubrynski.com
Marcin
Grzejszczak
@mgrzejszczak
toomuchcoding.blogspot.com

3. TDD on architectural level
@mgrzejszczak @jkubrynski

4. What is
Consumer Driven Contract
@mgrzejszczak @jkubrynski
● Server
● Consumer
● Contract

5. Consumer Driven Contract
benefits
@mgrzejszczak @jkubrynski

6. Example
@mgrzejszczak @jkubrynski

7. Example
@mgrzejszczak @jkubrynski

8. How to solve it
@mgrzejszczak @jkubrynski
● Consumer’s tests
● Server tests

9. Contract definition
@mgrzejszczak @jkubrynski
● Contract defines communication
● Your stub is your contract - verify it!
● Expose your stub to your consumers

10. Consumer Technology
@mgrzejszczak @jkubrynski
Wiremock
http://wiremock.org
testCompile 'com.github.tomakehurst:wiremock:1.53'
{
"request": {
"method": "GET",
"url": "/hello"
},
"response": {
"status": 200,
"body": "Hello world!",
"headers": { "Content-Type": "text/plain" }
}
}

11. Server Technology
@mgrzejszczak @jkubrynski
Accurate REST
https://github.com/Codearte/accurest
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath 'io.codearte.accurest:accurest-gradle-plugin:0.5.0'
}
}
apply plugin: 'accurest'

12. Server Technology
@mgrzejszczak @jkubrynski
Accurate REST
def shouldMarkClientAsNotFraud() {
given:
def request = given()
.header('Content-Type', 'application/frud+json')
.body('{"clientPesel":"12345678901",
"loanAmount":123.123}')
when:
def response = given().spec(request)
.put("/fraudcheck")
then:
response.statusCode == 200
response.header('Content-Type') == 'application/fraud+json'
and:
def responseBody = parseText(response.body.asString())
responseBody.fraudCheckStatus == "OK"
}

13. Example
@mgrzejszczak @jkubrynski

14. Live coding
@mgrzejszczak @jkubrynski

15. Q&A
@mgrzejszczak @jkubrynski
github.com/marcingrzejszczak/4developers_cdc_examples