Consumer driven contract testing

Consumer Driven Contract Testing
Mike van Vendeloo @mikevanvendeloo

@mikevanvendeloo
About me
Mike van Vendeloo
Software Craftsman
Scrum Master
Focussed on software quality and automation

@mikevanvendeloo
Agenda
1. Background
2. Consumer Driven Contract Testing
3. Spring Cloud Contract

@mikevanvendeloo
Consumer Driven Contracts to the rescue
Consumer Driven Contracts is a pattern that drives the
development of the Producer from its Consumers point of view.

@mikevanvendeloo
Terminology
A Contract is a collection of agreements between a client
(Consumer) and an API (Producer) that describes the
interactions that can take place between them.
Consumer: Service listening to messages or requesting API methods
Producer: Service sending messages or exposing an API
Contract: Agreement between producer and consumer how the API (method,
request and response) / message will look like

@mikevanvendeloo
Technology Radar
“The concept isn’t new, but with the mainstream
acceptance of microservices, we need to remind
people that consumer-driven contracts are an
essential part of a mature microservice testing
portfolio, enabling independent service
deployments.”

@mikevanvendeloo
Consumer Driven Contract Testing
“TDD on the architectural level”
“Use an API before implementing it”
-- Marcin Grzejszczak --

@mikevanvendeloo
Frameworks
Pact - https://docs.pact.io/
Pact-JVM - https://github.com/DiUS/pact-jvm
Karma-Pact - https://github.com/pact-foundation/karma-pact
Pacto - http://thoughtworks.github.io/pacto/
AccuRest - https://github.com/Codearte/accurest -> Spring Cloud Contract
And many more...

@mikevanvendeloo
Consumer
Spring Cloud Contract
Producer
A
P
I
Consumer

@mikevanvendeloo
Spring Cloud Contract
● Spring Cloud Contract Verifier
● Spring Cloud Contract Wiremock
● Spring Cloud Contract Stubrunner

@mikevanvendeloo
Contract DSL
package net.vanvendeloo.demos.comicbooks
org.springframework.cloud.contract.spec.Contract.make {
description(“”” Some explanation in given/when/then style “””)
request {
method 'PUT'
url '/comicbook'
body ([ title : ‘Game of drones’, isbn: ‘9789002259722’])
}
response {
status 201
}
}

@mikevanvendeloo
Contract
verifier tests
Producer side
Maven
repository
stubs.jar
contract
Producer
A
P
I
generate
generate

@mikevanvendeloo
You can easily compile Contracts to WireMock stubs mapping using standalone maven
command:
mvn org.springframework.cloud:spring-cloud-contract-maven-plugin:convert
Producer side - Wiremock

@mikevanvendeloo
{
"id" : "2656c2c0-64b1-4d54-8ccd-8b5db4304248",
"request" : {
"url" : "/comics",
"method" : "GET"
},
"response" : {
"status" : 200,
"body" : "[{"id":1,"name":"Suske en Wiske","comicBooks":[{"id":1,"title":"Game of
drones","isbn":"9789002259722","number":337}]}]",
"headers" : {
"Content-Type" : "application/json"
},
"transformers" : [ "response-template" ]
},
"uuid" : "2656c2c0-64b1-4d54-8ccd-8b5db4304248"
}
Producer side - Stubs

@mikevanvendeloo
<plugin>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-contract-maven-plugin</artifactId>
<version>${spring-cloud-contract.version}</version>
<extensions>true</extensions>
<configuration>
<packageWithBaseClasses>net.vanvendeloo.demo.comicbooks</packageWi
thBaseClasses>
</configuration>
</plugin>
Producer side - Generate tests and stubs

@mikevanvendeloo
package net.vanvendeloo.demo.cloudcontract.comiccollection;
import org.junit.Before;
import com.jayway.restassured.module.mockmvc.RestAssuredMockMvc;
public class ComicCollectionTestBase {
@Before
public void setup() {
RestAssuredMockMvc.standaloneSetup(new ComicCollectionController());
}
}
Producer side - Base class

@mikevanvendeloo
Consumer side
Maven
repository
stubs.jar
Consumer
Stub
runner
T
E
S
T
S
download

@mikevanvendeloo
Consumer side - Using stubs (1)
<dependency>
<artifactId>spring-cloud-starter-contract-stub-runner</artifactId>
<scope>test</scope>
</dependency>

@mikevanvendeloo
@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment=WebEnvironment.NONE)
@AutoConfigureStubRunner(ids =
{"net.vanvendeloo.demo.comicbooks:comic-collections-api:+:stubs:8090"
}, workOffline = true)
@DirtiesContext
public class ComicCollectionApplicationTest {
…
}
Consumer side - Using stubs (2)

@mikevanvendeloo
Advanced contracts - Regular expressions
org.springframework.cloud.contract.spec.Contract.make {
request {
method 'POST'
url '/comicbook/1'
headers { contentType(applicationJson()) }
body(
title: $(consumer(regex(‘[A-Za-z ]+)), producer('My title')),
isbn: $(consumer(regex('[0-9]{10}')), producer('1234567890'))
)
}
...

@mikevanvendeloo
Set properties in the body
value(consumer(...), producer(...))
$(consumer(...), producer(...))
Reuse of request information in the response
fromRequest().body(String jsonPath)
Advanced contracts - Dynamic properties

@mikevanvendeloo
Test matchers
jsonPath('$.isbn', byRegex(number()))
jsonPath('$.returned', byRegex(anyBoolean()))
jsonPath('$.returndate, byRegex(byDate()))
Results in testcode
assertThat(parsedJson.read("$.isbn", String.class)).matches("-?d*(.d+)?");
assertThat(parsedJson.read("$.returned", String.class)).matches("(true|false)");
assertThat(parsedJson.read("$.returndate",
String.class)).matches("(dddd)-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])");
Advanced contracts - Test matchers

@mikevanvendeloo
Ability to specify how the dynamic values should be generated by wiremock
jsonPath('$.isbn, byRegex(number()))
jsonPath('$.returned, byRegex(anyBoolean()))
jsonPath('$.returnDate, byDate())
{ "matchesJsonPath" : "$[?(@.isbn =~ /(-?d*(.d+)?)/)]"},
{ "matchesJsonPath" : "$[?(@.returned =~ /((true|false))/)]"},
{ "matchesJsonPath" : "$[?(@.returndate =~
/((dddd)-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01]))/)]"}
Advanced contracts - Stub matchers

@mikevanvendeloo
this.mockMvc.perform(post("/comicbooksearch")
.accept(MediaType.APPLICATION_JSON)
.contentType(MediaType.APPLICATION_JSON)
.content("{"number": 337 }"))
.andExpect(status().isOk())
.contentType(MediaType.valueOf("application/json"))
.stub("shouldReturnComicBook"))
// then Contract DSL documentation
.andDo(document("getComicBook",
SpringCloudContractRestDocs.dslContract()));
Advanced contracts - Generate from RestDocs

@mikevanvendeloo
Contract Repository
Sharing the contracts via a separate repository
<plugin>
<artifactId>spring-cloud-contract-maven-plugin</artifactId>
<configuration>
<contractsRepositoryUrl>http://link/to/your/nexus</contractsRepositoryUrl>
<contractDependency>
<groupId>net.vanvendeloo.demos.comiccollections</groupId>
<artifactId>contracts</artifactId>
</contractDependency>
</configuration>
</plugin>

@mikevanvendeloo
Contract Testing with messaging
Out of the box integration for using stubs with the following frameworks
● Spring Integration
● Spring Cloud Stream
● Apache Camel
● Spring AMQP

@mikevanvendeloo
Contract.make {
label 'return_comicbook_1'
input {
triggeredBy('bookReturnedTriggered()')
}
outputMessage {
sentTo('returnBook')
body('''{ "title" : "Game of drones" }''')
headers {
header('TITLE', 'Game of drones')
}
}
}
Contract for messages

@mikevanvendeloo
Conclusions
● Communication is still the most important thing!
● CDC frameworks are still in development
● Spring Cloud Contract
○ integrates well with the Spring ecosystem
○ ensures reusable stubs
○ in the future, will provide improved tooling for non-Java
users

@mikevanvendeloo
References
https://martinfowler.com/articles/consumerDrivenContracts.html
https://github.com/spring-cloud-samples/spring-cloud-contract-samples
https://www.youtube.com/watch?v=sAAklvxmPmk&t=547s

Consumer driven contract testing

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