# Spring Cloud Contract

Documentation Authors: Adam Dudczak, Mathias Düsterhöft, Marcin Grzejszczak, Dennis Kieselhorst, Jakub Kubryński, Karol Lassak, Olga Maciaszek-Sharma, Mariusz Smykuła, Dave Syer

1.0.4.RELEASE

## Spring Cloud Contract

What you always need is confidence in pushing new features into a new application or service in a distributed system. This project 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.

## Spring Cloud Contract WireMock

Modules giving you the possibility to use WireMock with different servers by using the "ambient" server embedded in a Spring Boot application. Check out the samples for more details.

Important | The Spring Cloud Release Train BOM imports `spring-cloud-contract-dependencies` which in turn has exclusions for the dependencies needed by WireMock. This might lead to a situation that even if you’re not using Spring Cloud Contract then your dependencies will be influenced anyways.

If you have a Spring Boot application that uses Tomcat as an embedded server, for example (the default with `spring-boot-starter-web`), then you can simply add `spring-cloud-contract-wiremock` to your classpath and add `@AutoConfigureWireMock` in order to be able to use Wiremock in your tests. Wiremock runs as a stub server and you can register stub behaviour using a Java API or via static JSON declarations as part of your test. Here’s a simple example:

    @RunWith(SpringRunner.class)
    @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
    @AutoConfigureWireMock(port = 0)
    public class WiremockForDocsTests {
    	// A service that calls out over HTTP
    	@Autowired private Service service;

    	// Using the WireMock APIs in the normal way:
    	@Test
    	public void contextLoads() throws Exception {
    		// Stubbing WireMock
    		stubFor(get(urlEqualTo("/resource"))
    				.willReturn(aResponse().withHeader("Content-Type", "text/plain").withBody("Hello World!")));
    		// We're asserting if WireMock responded properly
    		assertThat(this.service.go()).isEqualTo("Hello World!");
    	}

    }

To start the stub server on a different port use `@AutoConfigureWireMock(port=9999)` (for example), and for a random port use the value 0. The stub server port will be bindable in the test application context as "wiremock.server.port". Using `@AutoConfigureWireMock` adds a bean of type `WiremockConfiguration` to your test application context, where it will be cached in between methods and classes having the same context, just like for normal Spring integration tests.

### Registering Stubs Automatically

If you use `@AutoConfigureWireMock` then it will register WireMock JSON stubs from the file system or classpath, by default from `file:src/test/resources/mappings`. You can customize the locations using the `stubs` attribute in the annotation, which can be a resource pattern (ant-style) or a directory, in which case `*/.json` is appended. Example:

    @RunWith(SpringRunner.class)
    @SpringBootTest
    @AutoConfigureWireMock(stubs="classpath:/stubs")
    public class WiremockImportApplicationTests {

    	@Autowired
    	private Service service;

    	@Test
    	public void contextLoads() throws Exception {
    		assertThat(this.service.go()).isEqualTo("Hello World!");
    	}

    }

Note | Actually WireMock always loads mappings from `src/test/resources/mappings` as well as the custom locations in the stubs attribute. To change this behaviour you have to also specify a files root as described next.

### Using Files to Specify the Stub Bodies

WireMock can read response bodies from files on the classpath or file system. In that case you will see in the JSON DSL that the response has a "bodyFileName" instead of a (literal) "body". The files are resolved relative to a root directory `src/test/resources/__files` by default. To customize this location you can set the `files` attribute in the `@AutoConfigureWireMock` annotation to the location of the parent directory (i.e. the place `__files` is a subdirectory). You can use Spring resource notation to refer to `file:…​` or `classpath:…​` locations (but generic URLs are not supported). A list of values can be given and WireMock will resolve the first file that exists when it needs to find a response body.

Note | when you configure the `files` root, then it affects the automatic loading of stubs as well (they come from the root location in a subdirectory called "mappings"). The value of `files` has no effect on the stubs loaded explicitly from the `stubs` attribute.

### Alternative: Using JUnit Rules

For a more conventional WireMock experience, using JUnit `@Rules` to start and stop the server, just use the `WireMockSpring` convenience class to obtain an `Options` instance:

    @RunWith(SpringRunner.class)
    @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
    public class WiremockForDocsClassRuleTests {

    	// Start WireMock on some dynamic port
    	// for some reason `dynamicPort()` is not working properly
    	@ClassRule
    	public static WireMockClassRule wiremock = new WireMockClassRule(
    			WireMockSpring.options().dynamicPort());
    	// A service that calls out over HTTP to localhost:${wiremock.port}
    	@Autowired
    	private Service service;

    	// Using the WireMock APIs in the normal way:
    	@Test
    	public void contextLoads() throws Exception {
    		// Stubbing WireMock
    		wiremock.stubFor(get(urlEqualTo("/resource"))
    				.willReturn(aResponse().withHeader("Content-Type", "text/plain").withBody("Hello World!")));
    		// We're asserting if WireMock responded properly
    		assertThat(this.service.go()).isEqualTo("Hello World!");
    	}

    }

The use `@ClassRule` means that the server will shut down after all the methods in this class.

## WireMock and Spring MVC Mocks

Spring Cloud Contract provides a convenience class that can load JSON WireMock stubs into a Spring `MockRestServiceServer`. Here’s an example:

    @RunWith(SpringRunner.class)
    @SpringBootTest(webEnvironment = WebEnvironment.NONE)
    public class WiremockForDocsMockServerApplicationTests {

    	@Autowired
    	private RestTemplate restTemplate;

    	@Autowired
    	private Service service;

    	@Test
    	public void contextLoads() throws Exception {
    		// will read stubs classpath
    		MockRestServiceServer server = WireMockRestServiceServer.with(this.restTemplate)
    				.baseUrl("http://example.org").stubs("classpath:/stubs/resource.json")
    				.build();
    		// We're asserting if WireMock responded properly
    		assertThat(this.service.go()).isEqualTo("Hello World");
    		server.verify();
    	}
    }

The `baseUrl` is prepended to all mock calls, and the `stubs()` method takes a stub path resource pattern as an argument. So in this example the stub defined at `/stubs/resource.json` is loaded into the mock server, so if the `RestTemplate` is asked to visit `http://example.org/` it will get the responses as declared there. More than one stub pattern can be specified, and each one can be a directory (for a recursive list of all ".json"), or a fixed filename (like in the example above) or an ant-style pattern. The JSON format is the normal WireMock format which you can read about in the WireMock website.

Currently we support Tomcat, Jetty and Undertow as Spring Boot embedded servers, and Wiremock itself has "native" support for a particular version of Jetty (currently 9.2). To use the native Jetty you need to add the native wiremock dependencies and exclude the Spring Boot container if there is one.

## Generating Stubs using RestDocs

Spring RestDocs can be used to generate documentation (e.g. in asciidoctor format) for an HTTP API with Spring MockMvc or RestEasy. At the same time as you generate documentation for your API, you can also generate WireMock stubs, by using Spring Cloud Contract WireMock. Just write your normal RestDocs test cases and use `@AutoConfigureRestDocs` to have stubs automatically in the restdocs output directory. For example:

    @RunWith(SpringRunner.class)
    @SpringBootTest
    @AutoConfigureRestDocs(outputDir = "target/snippets")
    @AutoConfigureMockMvc
    public class ApplicationTests {

    	@Autowired
    	private MockMvc mockMvc;

    	@Test
    	public void contextLoads() throws Exception {
    		mockMvc.perform(get("/resource"))
    				.andExpect(content().string("Hello World"))
    				.andDo(document("resource"));
    	}
    }

From this test will be generated a WireMock stub at "target/snippets/stubs/resource.json". It matches all GET requests to the "/resource" path.

Without any additional configuration this will create a stub with a request matcher for the HTTP method and all headers except "host" and "content-length". To match the request more precisely, for example to match the body of a POST or PUT, we need to explicitly create a request matcher. This will do two things: 1) create a stub that only matches the way you specify, 2) assert that the request in the test case also matches the same conditions.

The main entry point for this is `WireMockRestDocs.verify()` which can be used as a substitute for the `document()` convenience method. For example:

    @RunWith(SpringRunner.class)
    @SpringBootTest
    @AutoConfigureRestDocs(outputDir = "target/snippets")
    @AutoConfigureMockMvc
    public class ApplicationTests {

    	@Autowired
    	private MockMvc mockMvc;

    	@Test
    	public void contextLoads() throws Exception {
    		mockMvc.perform(post("/resource")
                    .content("{\"id\":\"123456\",\"message\":\"Hello World\"}"))
    				.andExpect(status().isOk())
    				.andDo(verify().jsonPath("$.id")
                            .stub("resource"));
    	}
    }

So this contract is saying: any valid POST with an "id" field will get back an the same response as in this test. You can chain together calls to `.jsonPath()` to add additional matchers. The JayWay documentation can help you to get up to speed with JSON Path if it is unfamiliar to you.

Instead of the `jsonPath` and `contentType` convenience methods, you can also use the WireMock APIs to verify the request matches the created stub. Example:

    @Test
    public void contextLoads() throws Exception {
    	mockMvc.perform(post("/resource")
                   .content("{\"id\":\"123456\",\"message\":\"Hello World\"}"))
    			.andExpect(status().isOk())
    			.andDo(verify()
    					.wiremock(WireMock.post(
    						urlPathEquals("/resource"))
    						.withRequestBody(matchingJsonPath("$.id"))
                           .stub("post-resource"));
    }

The WireMock API is rich - you can match headers, query parameters, and request body by regex as well as by json path - so this can useful to create stubs with a wider range of parameters. The above example will generate a stub something like this:

post-resource.json

    {
      "request" : {
        "url" : "/resource",
        "method" : "POST",
        "bodyPatterns" : [ {
          "matchesJsonPath" : "$.id"
        }]
      },
      "response" : {
        "status" : 200,
        "body" : "Hello World",
        "headers" : {
          "X-Application-Context" : "application:-1",
          "Content-Type" : "text/plain"
        }
      }
    }

Note | You can use either the `wiremock()` method or the `jsonPath()` and `contentType()` methods to create request matchers, but not both.

On the consumer side, assuming the `resource.json` generated above is available on the classpath, you can create a stub using WireMock in a number of different ways, including as described above using `@AutoConfigureWireMock(stubs="classpath:resource.json")`.

## Generating Contracts using RestDocs

Another thing that can be generated with Spring RestDocs is the Spring Cloud Contract DSL file and documentation. If you combine that with Spring Cloud WireMock then you’re getting both the contracts and stubs.

Tip | You might wonder why this functionality is in the WireMock module. Come to think of it, it does make sense since it makes little sense to generate only contracts and not generate the stubs. That’s why we suggest to do both.

Let’s imagine the following test:

    		this.mockMvc.perform(post("/foo")
    					.accept(MediaType.APPLICATION_PDF)
    					.accept(MediaType.APPLICATION_JSON)
    					.contentType(MediaType.APPLICATION_JSON)
    					.content("{\"foo\": 23 }"))
    				.andExpect(status().isOk())
    				.andExpect(content().string("bar"))
    				// first WireMock
    				.andDo(WireMockRestDocs.verify()
    						.jsonPath("$[?(@.foo >= 20)]")
    						.contentType(MediaType.valueOf("application/json"))
    						.stub("shouldGrantABeerIfOldEnough"))
    				// then Contract DSL documentation
    				.andDo(document("index", SpringCloudContractRestDocs.dslContract()));

This will lead in the creation of the stub as presented in the previous section, contract will get generated and a documentation file too.

The contract will be called `index.groovy` and look more like this.

    import org.springframework.cloud.contract.spec.Contract

    Contract.make {
        request {
            method 'POST'
            url 'http://localhost:8080/foo'
            body('''
                {"foo": 23 }
            ''')
            headers {
                header('''Accept''', '''application/json''')
                header('''Content-Type''', '''application/json''')
                header('''Host''', '''localhost:8080''')
                header('''Content-Length''', '''12''')
            }
        }
        response {
            status 200
            body('''
            bar
            ''')
            headers {
                header('''Content-Type''', '''application/json;charset=UTF-8''')
                header('''Content-Length''', '''3''')
            }
            testMatchers {
                jsonPath('$[?(@.foo >= 20)]', byType())
            }
        }
    }

the generated document (example for Asciidoc) will contain a formatted contract (the location of this file would be `index/dsl-contract.adoc`).

## Spring Cloud Contract Verifier

### Introduction

Important | The documentation to the deprecated Accurest project in version 1.1.0 is available here.

Tip | The Accurest project was initially started by Marcin Grzejszczak and Jakub Kubrynski (codearte.io)

Just to make long story short - Spring Cloud Contract Verifier is a tool that enables Consumer Driven Contract (CDC) development of JVM-based applications. It is shipped with Contract Definition Language (DSL). Contract definitions are used to produce following resources:

- JSON stub definitions to be used by WireMock when doing integration testing on the client code (client tests). Test code must still be written by hand, test data is produced by Spring Cloud Contract Verifier.

- Messaging routes if you’re using one. We’re integrating with Spring Integration, Spring Cloud Stream, Spring AMQP and Apache Camel. You can however set your own integrations if you want to

- Acceptance tests (in JUnit or Spock) used to verify if server-side implementation of the API is compliant with the contract (server tests). Full test is generated by Spring Cloud Contract Verifier.

Spring Cloud Contract Verifier moves TDD to the level of software architecture.

#### Spring Cloud Contract video

You can check out the video from the Warsaw JUG about Spring Cloud Contract:

#### Why?

Let us assume that we have a system comprising of multiple microservices:

##### Testing issues

If we wanted to test the application in top left corner if it can communicate with other services then we could do one of two things:

- deploy all microservices and perform end to end tests

- mock other microservices in unit / integration tests

Both have their advantages but also a lot of disadvantages. Let’s focus on the latter.

Deploy all microservices and perform end to end tests

Advantages:

- simulates production

- tests real communication between services

Disadvantages:

- to test one microservice we would have to deploy 6 microservices, a couple of databases etc.

- the environment where the tests would be conducted would be locked for a single suite of tests (i.e. nobody else would be able to run the tests in the meantime).

- long to run

- very late feedback

- extremely hard to debug

Mock other microservices in unit / integration tests

Advantages:

- very fast feedback

- no infrastructure requirements

Disadvantages:

- the implementor of the service creates stubs thus they might have nothing to do with the reality

- you can go to production with passing tests and failing production

To solve the aforementioned issues Spring Cloud Contract Verifier with Stub Runner were created. Their main idea is to give you very fast feedback, without the need to set up the whole world of microservices.

If you work on stubs then the only applications you need are those that your application is using directly.

Spring Cloud Contract Verifier gives you the certainty that the stubs that you’re using were created by the service that you’re calling. Also if you can use them it means that they were tested against the producer’s side. In other words - you can trust those stubs.

#### Purposes

The main purposes of Spring Cloud Contract Verifier with Stub Runner are:

- to ensure that WireMock / Messaging stubs (used when developing the client) are doing exactly what actual server-side implementation will do,

- to promote ATDD method and Microservices architectural style,

- to provide a way to publish changes in contracts that are immediately visible on both sides,

- to generate boilerplate test code used on the server side.

Important

Spring Cloud Contract Verifier’s purpose is NOT to start writing business features in the contracts. Let’s assume that we have a business use case of fraud check. If a user can be a fraud for 100 different reasons, we would assume that you would create 2 contracts. One for the positive and one for the negative fraud case. Contract tests are used to test contracts between applications and not to simulate full behaviour.

#### Client Side

During the tests you want to have a WireMock instance / Messaging route up and running that simulates the service Y. You would like to feed that instance with a proper stub definition. That stub definition would need to be valid and should also be reusable on the server side.

Summing it up: On this side, in the stub definition, you can use patterns for request stubbing and you need exact values for responses.

#### Server Side

Being a service Y since you are developing your stub, you need to be sure that it’s actually resembling your concrete implementation. You can’t have a situation where your stub acts in one way and your application on production behaves in a different way.

That’s why from the provided stub acceptance tests will be generated that will ensure that your application behaves in the same way as you define in your stub.

Summing it up: On this side, in the stub definition, you need exact values as request and can use patterns/methods for response verification.

#### Step by step guide to CDC

Let’s take an example of Fraud Detection and Loan Issuance process. The business scenario is such that we want to issue loans to people but don’t want them to steal the money from us. The current implementation of our system grants loans to everybody.

Let’s assume that the `Loan Issuance` is a client to the `Fraud Detection` server. In the current sprint we are required to develop a new feature - if a client wants to borrow too much money then we mark him as fraud.

Technical remark - Fraud Detection will have artifact id `http-server`, Loan Issuance `http-client` and both have group id `com.example`.

Social remark - both client and server development teams need to communicate directly and discuss changes while going through the process. CDC is all about communication.

The server side code is available here and the client side code here.

Tip | In this case the ownership of the contracts lays on the producer side. It means that physically all the contract are present in the producer’s repository

##### Technical note

If using the SNAPSHOT / Milestone / Release Candidate versions please add the following section to your

Maven

    <repositories>
    	<repository>
    		<id>spring-snapshots</id>
    		<name>Spring Snapshots</name>
    		<url>https://repo.spring.io/snapshot</url>
    		<snapshots>
    			<enabled>true</enabled>
    		</snapshots>
    	</repository>
    	<repository>
    		<id>spring-milestones</id>
    		<name>Spring Milestones</name>
    		<url>https://repo.spring.io/milestone</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</repository>
    	<repository>
    		<id>spring-releases</id>
    		<name>Spring Releases</name>
    		<url>https://repo.spring.io/release</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</repository>
    </repositories>
    <pluginRepositories>
    	<pluginRepository>
    		<id>spring-snapshots</id>
    		<name>Spring Snapshots</name>
    		<url>https://repo.spring.io/snapshot</url>
    		<snapshots>
    			<enabled>true</enabled>
    		</snapshots>
    	</pluginRepository>
    	<pluginRepository>
    		<id>spring-milestones</id>
    		<name>Spring Milestones</name>
    		<url>https://repo.spring.io/milestone</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</pluginRepository>
    	<pluginRepository>
    		<id>spring-releases</id>
    		<name>Spring Releases</name>
    		<url>https://repo.spring.io/release</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</pluginRepository>
    </pluginRepositories>

Gradle

    repositories {
    	mavenCentral()
    	mavenLocal()
    	maven { url "http://repo.spring.io/snapshot" }
    	maven { url "http://repo.spring.io/milestone" }
    	maven { url "http://repo.spring.io/release" }
    }

##### Consumer side (Loan Issuance)

As a developer of the Loan Issuance service (a consumer of the Fraud Detection server):

start doing TDD by writing a test to your feature

    @Test
    public void shouldBeRejectedDueToAbnormalLoanAmount() {
    	// given:
    	LoanApplication application = new LoanApplication(new Client("1234567890"),
    			99999);
    	// when:
    	LoanApplicationResult loanApplication = service.loanApplication(application);
    	// then:
    	assertThat(loanApplication.getLoanApplicationStatus())
    			.isEqualTo(LoanApplicationStatus.LOAN_APPLICATION_REJECTED);
    	assertThat(loanApplication.getRejectionReason()).isEqualTo("Amount too high");
    }

We’ve just written a test of our new feature. If a loan application for a big amount is received we should reject that loan application with some description.

write the missing implementation

At some point in time you need to send a request to the Fraud Detection service. Let’s assume that we’d like to send the request containing the id of the client and the amount he wants to borrow from us. We’d like to send it to the `/fraudcheck` url via the `PUT` method.

    ResponseEntity<FraudServiceResponse> response =
    		restTemplate.exchange("http://localhost:" + port + "/fraudcheck", HttpMethod.PUT,
    				new HttpEntity<>(request, httpHeaders),
    				FraudServiceResponse.class);

For simplicity we’ve hardcoded the port of the Fraud Detection service at `8080` and our application is running on `8090`.

If we’d start the written test it would obviously break since we have no service running on port `8080`.

clone the Fraud Detection service repository locally

We’ll start playing around with the server side contract. That’s why we need to first clone it.

    git clone https://your-git-server.com/server-side.git local-http-server-repo

define the contract locally in the repo of Fraud Detection service

As consumers we need to define what exactly we want to achieve. We need to formulate our expectations. That’s why we write the following contract.

Important | We’re placing the contract under `src/test/resources/contract/fraud` folder. The `fraud` folder is important cause we’ll reference that folder in the producer’s test base class name.

    package contracts

    org.springframework.cloud.contract.spec.Contract.make {
    	request { // (1)
    		method 'PUT' // (2)
    		url '/fraudcheck' // (3)
    		body([ // (4)
    			   clientId: $(regex('[0-9]{10}')),
    			   loanAmount: 99999
    		])
    		headers { // (5)
    			contentType('application/vnd.fraud.v1+json')
    		}
    	}
    	response { // (6)
    		status 200 // (7)
    		body([ // (8)
    			   fraudCheckStatus: "FRAUD",
    			   rejectionReason: "Amount too high"
    		])
    		headers { // (9)
    			contentType('application/vnd.fraud.v1+json')
    		}
    	}
    }

    /*
    Since we don't want to force on the user to hardcode values of fields that are dynamic
    (timestamps, database ids etc.), one can parametrize those entries. If you wrap your field's
     value in a `$(...)` or `value(...)` and provide a dynamic value of a field then
     the concrete value will be generated for you. If you want to be really explicit about
     which side gets which value you can do that by using the `value(consumer(...), producer(...))` notation.
     That way what's present in the `consumer` section will end up in the produced stub. What's
     there in the `producer` will end up in the autogenerated test. If you provide only the
     regular expression side without the concrete value then Spring Cloud Contract will generate one for you.

    From the Consumer perspective, when shooting a request in the integration test:

    (1) - If the consumer sends a request
    (2) - With the "PUT" method
    (3) - to the URL "/fraudcheck"
    (4) - with the JSON body that
     * has a field `clientId` that matches a regular expression `[0-9]{10}`
     * has a field `loanAmount` that is equal to `99999`
    (5) - with header `Content-Type` equal to `application/vnd.fraud.v1+json`
    (6) - then the response will be sent with
    (7) - status equal `200`
    (8) - and JSON body equal to
     { "fraudCheckStatus": "FRAUD", "rejectionReason": "Amount too high" }
    (9) - with header `Content-Type` equal to `application/vnd.fraud.v1+json`

    From the Producer perspective, in the autogenerated producer-side test:

    (1) - A request will be sent to the producer
    (2) - With the "PUT" method
    (3) - to the URL "/fraudcheck"
    (4) - with the JSON body that
     * has a field `clientId` that will have a generated value that matches a regular expression `[0-9]{10}`
     * has a field `loanAmount` that is equal to `99999`
    (5) - with header `Content-Type` equal to `application/vnd.fraud.v1+json`
    (6) - then the test will assert if the response has been sent with
    (7) - status equal `200`
    (8) - and JSON body equal to
     { "fraudCheckStatus": "FRAUD", "rejectionReason": "Amount too high" }
    (9) - with header `Content-Type` matching `application/vnd.fraud.v1+json.*`
     */

The Contract is written using a statically typed Groovy DSL. You might be wondering what are those `value(client(…​), server(…​))` parts. By using this notation Spring Cloud Contract allows you to define parts of a JSON / URL / etc. which are dynamic. In case of an identifier or a timestamp you don’t want to hardcode a value. You want to allow some different ranges of values. That’s why for the consumer side you can set regular expressions matching those values. You can provide the body either by means of a map notation or String with interpolations. Consult the docs for more information. We highly recommend using the map notation!

Tip | It’s really important that you understand the map notation to set up contracts. Please read the Groovy docs regarding JSON

The aforementioned contract is an agreement between two sides that:

- if an HTTP request is sent with

  - a method `PUT` on an endpoint `/fraudcheck`

  - JSON body with `clientPesel` matching the regular expression `[0-9]{10}` and `loanAmount` equal to `99999`

  - and with a header `Content-Type` equal to `application/vnd.fraud.v1+json`

- then an HTTP response would be sent to the consumer that

  - has status `200`

  - contains JSON body with the `fraudCheckStatus` field containing a value `FRAUD` and the `rejectionReason` field having value `Amount too high`

  - and a `Content-Type` header with a value of `application/vnd.fraud.v1+json`

Once we’re ready to check the API in practice in the integration tests we need to just install the stubs locally

add the Spring Cloud Contract Verifier plugin

We can add either Maven or Gradle plugin - in this example we’ll show how to add Maven. First we need to add the `Spring Cloud Contract` BOM.

    <dependencyManagement>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-dependencies</artifactId>
    			<version>${spring-cloud-dependencies.version}</version>
    			<type>pom</type>
    			<scope>import</scope>
    		</dependency>
    	</dependencies>
    </dependencyManagement>

Next, the `Spring Cloud Contract Verifier` Maven plugin

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<version>${spring-cloud-contract.version}</version>
    	<extensions>true</extensions>
    	<configuration>
    		<packageWithBaseClasses>com.example.fraud</packageWithBaseClasses>
    	</configuration>
    </plugin>

Since the plugin was added we get the `Spring Cloud Contract Verifier` features which from the provided contracts:

- generate and run tests

- produce and install stubs

We don’t want to generate tests since we, as consumers, want only to play with the stubs. That’s why we need to skip the tests generation and execution. When we execute:

    cd local-http-server-repo
    ./mvnw clean install -DskipTests

In the logs we’ll see something like this:

    [INFO] --- spring-cloud-contract-maven-plugin:1.0.0.BUILD-SNAPSHOT:generateStubs (default-generateStubs) @ http-server ---
    [INFO] Building jar: /some/path/http-server/target/http-server-0.0.1-SNAPSHOT-stubs.jar
    [INFO]
    [INFO] --- maven-jar-plugin:2.6:jar (default-jar) @ http-server ---
    [INFO] Building jar: /some/path/http-server/target/http-server-0.0.1-SNAPSHOT.jar
    [INFO]
    [INFO] --- spring-boot-maven-plugin:1.4.0.BUILD-SNAPSHOT:repackage (default) @ http-server ---
    [INFO]
    [INFO] --- maven-install-plugin:2.5.2:install (default-install) @ http-server ---
    [INFO] Installing /some/path/http-server/target/http-server-0.0.1-SNAPSHOT.jar to /path/to/your/.m2/repository/com/example/http-server/0.0.1-SNAPSHOT/http-server-0.0.1-SNAPSHOT.jar
    [INFO] Installing /some/path/http-server/pom.xml to /path/to/your/.m2/repository/com/example/http-server/0.0.1-SNAPSHOT/http-server-0.0.1-SNAPSHOT.pom
    [INFO] Installing /some/path/http-server/target/http-server-0.0.1-SNAPSHOT-stubs.jar to /path/to/your/.m2/repository/com/example/http-server/0.0.1-SNAPSHOT/http-server-0.0.1-SNAPSHOT-stubs.jar

This line is extremely important

    [INFO] Installing /some/path/http-server/target/http-server-0.0.1-SNAPSHOT-stubs.jar to /path/to/your/.m2/repository/com/example/http-server/0.0.1-SNAPSHOT/http-server-0.0.1-SNAPSHOT-stubs.jar

It’s confirming that the stubs of the `http-server` have been installed in the local repository.

run the integration tests

In order to profit from the Spring Cloud Contract Stub Runner functionality of automatic stub downloading you have to do the following in our consumer side project (`Loan Application service`).

Add the `Spring Cloud Contract` BOM

    <dependencyManagement>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-dependencies</artifactId>
    			<version>${spring-cloud-dependencies.version}</version>
    			<type>pom</type>
    			<scope>import</scope>
    		</dependency>
    	</dependencies>
    </dependencyManagement>

Add the dependency to `Spring Cloud Contract Stub Runner`

    <dependency>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-starter-contract-stub-runner</artifactId>
    	<scope>test</scope>
    </dependency>

Annotate your test class with `@AutoConfigureStubRunner`. In the annotation provide the group id and artifact id for the Stub Runner to download stubs of your collaborators. Also provide the offline work switch since you’re playing with the collaborators offline (optional step).

    @RunWith(SpringRunner.class)
    @SpringBootTest(webEnvironment=WebEnvironment.NONE)
    @AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:stubs:6565"}, workOffline = true)
    @DirtiesContext
    public class LoanApplicationServiceTests {

Now if you run your tests you’ll see sth like this:

    2016-07-19 14:22:25.403  INFO 41050 --- [           main] o.s.c.c.stubrunner.AetherStubDownloader  : Desired version is + - will try to resolve the latest version
    2016-07-19 14:22:25.438  INFO 41050 --- [           main] o.s.c.c.stubrunner.AetherStubDownloader  : Resolved version is 0.0.1-SNAPSHOT
    2016-07-19 14:22:25.439  INFO 41050 --- [           main] o.s.c.c.stubrunner.AetherStubDownloader  : Resolving artifact com.example:http-server:jar:stubs:0.0.1-SNAPSHOT using remote repositories []
    2016-07-19 14:22:25.451  INFO 41050 --- [           main] o.s.c.c.stubrunner.AetherStubDownloader  : Resolved artifact com.example:http-server:jar:stubs:0.0.1-SNAPSHOT to /path/to/your/.m2/repository/com/example/http-server/0.0.1-SNAPSHOT/http-server-0.0.1-SNAPSHOT-stubs.jar
    2016-07-19 14:22:25.465  INFO 41050 --- [           main] o.s.c.c.stubrunner.AetherStubDownloader  : Unpacking stub from JAR [URI: file:/path/to/your/.m2/repository/com/example/http-server/0.0.1-SNAPSHOT/http-server-0.0.1-SNAPSHOT-stubs.jar]
    2016-07-19 14:22:25.475  INFO 41050 --- [           main] o.s.c.c.stubrunner.AetherStubDownloader  : Unpacked file to [/var/folders/0p/xwq47sq106x1_g3dtv6qfm940000gq/T/contracts100276532569594265]
    2016-07-19 14:22:27.737  INFO 41050 --- [           main] o.s.c.c.stubrunner.StubRunnerExecutor    : All stubs are now running RunningStubs [namesAndPorts={com.example:http-server:0.0.1-SNAPSHOT:stubs=8080}]

Which means that Stub Runner has found your stubs and started a server for app with group id `com.example`, artifact id `http-server` with version `0.0.1-SNAPSHOT` of the stubs and with `stubs` classifier on port `8080`.

file a PR

What we did until now is an iterative process. We can play around with the contract, install it locally and work on the consumer side until we’re happy with the contract.

Once we’re satisfied with the results and the test passes publish a PR to the server side. Currently the consumer side work is done.

##### Producer side (Fraud Detection server)

As a developer of the Fraud Detection server (a server to the Loan Issuance service):

initial implementation

As a reminder here you can see the initial implementation

    @RequestMapping(
    		value = "/fraudcheck",
    		method = PUT,
    		consumes = FRAUD_SERVICE_JSON_VERSION_1,
    		produces = FRAUD_SERVICE_JSON_VERSION_1)
    public FraudCheckResult fraudCheck(@RequestBody FraudCheck fraudCheck) {
    return new FraudCheckResult(FraudCheckStatus.OK, NO_REASON);
    }

take over the PR

    git checkout -b contract-change-pr master
    git pull https://your-git-server.com/server-side-fork.git contract-change-pr

You have to add the dependencies needed by the autogenerated tests

    	<dependency>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-starter-contract-verifier</artifactId>
    	<scope>test</scope>
    </dependency>

In the configuration of the Maven plugin we passed the `packageWithBaseClasses` property

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<version>${spring-cloud-contract.version}</version>
    	<extensions>true</extensions>
    	<configuration>
    		<packageWithBaseClasses>com.example.fraud</packageWithBaseClasses>
    	</configuration>
    </plugin>

Important

We’ve decided to use the "convention based" naming by setting the `packageWithBaseClasses` property. That means that 2 last packages will be combined into a name of the base test class. In our case the contracts were placed under `src/test/resources/contract/fraud`. Since we don’t have 2 packages starting from the `contracts` folder we’re picking only one which is `fraud`. We’re adding the `Base` suffix and we’re capitalizing `fraud`. That gives us the `FraudBase` test class name.

That’s because all the generated tests will extend that class. Over there you can set up your Spring Context or whatever is necessary. In our case we’re using Rest Assured MVC to start the server side `FraudDetectionController`.

    package com.example.fraud;

    import com.example.fraud.FraudDetectionController;
    import com.jayway.restassured.module.mockmvc.RestAssuredMockMvc;

    import org.junit.Before;

    public class FraudBase {

    	@Before
    	public void setup() {
    		RestAssuredMockMvc.standaloneSetup(new FraudDetectionController());
    	}

    	public void assertThatRejectionReasonIsNull(Object rejectionReason) {
    		assert rejectionReason == null;
    	}
    }

Now, if you run the `./mvnw clean install` you would get sth like this:

    Results :

    Tests in error:
      ContractVerifierTest.validate_shouldMarkClientAsFraud:32 » IllegalState Parsed...

That’s because you have a new contract from which a test was generated and it failed since you haven’t implemented the feature. The autogenerated test would look like this:

    @Test
    public void validate_shouldMarkClientAsFraud() throws Exception {
        // given:
            MockMvcRequestSpecification request = given()
                    .header("Content-Type", "application/vnd.fraud.v1+json")
                    .body("{\"clientPesel\":\"1234567890\",\"loanAmount\":99999}");

        // when:
            ResponseOptions response = given().spec(request)
                    .put("/fraudcheck");

        // then:
            assertThat(response.statusCode()).isEqualTo(200);
            assertThat(response.header("Content-Type")).matches("application/vnd.fraud.v1.json.*");
        // and:
            DocumentContext parsedJson = JsonPath.parse(response.getBody().asString());
            assertThatJson(parsedJson).field("fraudCheckStatus").matches("[A-Z]{5}");
            assertThatJson(parsedJson).field("rejectionReason").isEqualTo("Amount too high");
    }

As you can see all the `producer()` parts of the Contract that were present in the `value(consumer(…​), producer(…​))` blocks got injected into the test.

What’s important here to note is that on the producer side we also are doing TDD. We have expectations in form of a test. This test is shooting a request to our own application to an URL, headers and body defined in the contract. It also is expecting very precisely defined values in the response. In other words you have is your `red` part of `red`, `green` and `refactor`. Time to convert the `red` into the `green`.

write the missing implementation

Now since we now what is the expected input and expected output let’s write the missing implementation.

    @RequestMapping(
    		value = "/fraudcheck",
    		method = PUT,
    		consumes = FRAUD_SERVICE_JSON_VERSION_1,
    		produces = FRAUD_SERVICE_JSON_VERSION_1)
    public FraudCheckResult fraudCheck(@RequestBody FraudCheck fraudCheck) {
    if (amountGreaterThanThreshold(fraudCheck)) {
    	return new FraudCheckResult(FraudCheckStatus.FRAUD, AMOUNT_TOO_HIGH);
    }
    return new FraudCheckResult(FraudCheckStatus.OK, NO_REASON);
    }

If we execute `./mvnw clean install` again the tests will pass. Since the `Spring Cloud Contract Verifier` plugin adds the tests to the `generated-test-sources` you can actually run those tests from your IDE.

deploy your app

Once you’ve finished your work it’s time to deploy your change. First merge the branch

    git checkout master
    git merge --no-ff contract-change-pr
    git push origin master

Then we assume that your CI would run sth like `./mvnw clean deploy` which would publish both the application and the stub artifcats.

##### Consumer side (Loan Issuance) final step

As a developer of the Loan Issuance service (a consumer of the Fraud Detection server):

merge branch to master

    git checkout master
    git merge --no-ff contract-change-pr

work online

Now you can disable the offline work for Spring Cloud Contract Stub Runner ad provide where the repository with your stubs is placed. At this moment the stubs of the server side will be automatically downloaded from Nexus / Artifactory. You can switch off the value of the `workOffline` parameter in your annotation. Below you can see an example of achieving the same by changing the properties.

    stubrunner:
      ids: 'com.example:http-server-dsl:+:stubs:8080'
      repositoryRoot: http://repo.spring.io/libs-snapshot

And that’s it!

#### Dependencies

The best way to add the dependencies is to just use the proper `starter` dependency.

For `stub-runner` use `spring-cloud-starter-stub-runner` and when you’re using a plugin just add `spring-cloud-starter-contract-verifier`.

#### Additional links

Below you can find some resources related to Spring Cloud Contract Verifier and Stub Runner. Note that some can be outdated since the Spring Cloud Contract Verifier project is under constant development.

##### Readings

- Slides from Marcin Grzejszczak’s talk about Accurest

- Accurest related articles from Marcin Grzejszczak’s blog

- Spring Cloud Contract related articles from Marcin Grzejszczak’s blog

- Groovy docs regarding JSON

#### Samples

Here you can find some samples.

### FAQ

#### Why use Spring Cloud Contract Verifier and not X ?

For the time being Spring Cloud Contract Verifier is a JVM based tool. So it could be your first pick when you’re already creating software for the JVM. This project has a lot of really interesting features but especially quite a few of them definitely make Spring Cloud Contract Verifier stand out on the "market" of Consumer Driven Contract (CDC) tooling. Out of many the most interesting are:

- Possibility to do CDC with messaging

- Clear and easy to use, statically typed DSL

- Possibility to copy paste your current JSON file to the contract and only edit its elements

- Automatic generation of tests from the defined Contract

- Stub Runner functionality - the stubs are automatically downloaded at runtime from Nexus / Artifactory

- Spring Cloud integration - no discovery service is needed for integration tests

#### What is this value(consumer(), producer()) ?

One of the biggest challenges related to stubs is their reusability. Only if they can be vastly used, will they serve their purpose. What typically makes that difficult are the hard-coded values of request / response elements. For example dates or ids. Imagine the following JSON request

    {
        "time" : "2016-10-10 20:10:15",
        "id" : "9febab1c-6f36-4a0b-88d6-3b6a6d81cd4a",
        "body" : "foo"
    }

and JSON response

    {
        "time" : "2016-10-10 21:10:15",
        "id" : "c4231e1f-3ca9-48d3-b7e7-567d55f0d051",
        "body" : "bar"
    }

Imagine the pain required to set proper value of the `time` field (let’s assume that this content is generated by the database) by changing the clock in the system or providing stub implementations of data providers. The same is related to the field called `id`. Will you create a stubbed implementation of UUID generator? Makes little sense…​

So as a consumer you would like to send a request that matches any form of a time or any UUID. That way your system will work as usual - will generate data and you won’t have to stub anything out. Let’s assume that in case of the aforementioned JSON the most important part is the `body` field. You can focus on that and provide matching for other fields. In other words you would like the stub to work like this:

    {
        "time" : "SOMETHING THAT MATCHES TIME",
        "id" : "SOMETHING THAT MATCHES UUID",
        "body" : "foo"
    }

As far as the response goes as a consumer you need a concrete value that you can operate on. So such a JSON is valid

    {
        "time" : "2016-10-10 21:10:15",
        "id" : "c4231e1f-3ca9-48d3-b7e7-567d55f0d051",
        "body" : "bar"
    }

As you could see in the previous sections we generate tests from contracts. So from the producer’s side the situation looks much different. We’re parsing the provided contract and in the test we want to send a real request to your endpoints. So for the case of a producer for the request we can’t have any sort of matching. We need concrete values that the producer’s backend can work on. Such a JSON would be a valid one:

    {
        "time" : "2016-10-10 20:10:15",
        "id" : "9febab1c-6f36-4a0b-88d6-3b6a6d81cd4a",
        "body" : "foo"
    }

On the other hand from the point of view of the validity of the contract the response doesn’t necessarily have to contain concrete values of `time` or `id`. Let’s say that you generate those on the producer side - again, you’d have to do a lot of stubbing to ensure that you always return the same values. That’s why from the producer’s side what you might want is the following response:

    {
        "time" : "SOMETHING THAT MATCHES TIME",
        "id" : "SOMETHING THAT MATCHES UUID",
        "body" : "bar"
    }

How can you then provide one time a matcher for the consumer and a concrete value for the producer and vice versa? In Spring Cloud Contract we’re allowing you to provide a dynamic value. That means that it can differ for both sides of the communication. You can pass the values:

Either via the `value` method

    value(consumer(...), producer(...))
    value(stub(...), test(...))
    value(client(...), server(...))

or using the `$()` method

    $(consumer(...), producer(...))
    $(stub(...), test(...))
    $(client(...), server(...))

You can read more about this in the Contract DSL section.

Calling `value()` or `$()` tells Spring Cloud Contract that you will be passing a dynamic value. Inside the `consumer()` method you pass the value that should be used on the consumer side (in the generated stub). Inside the `producer()` method you pass the value that should be used on the producer side (in the generated test).

Tip | If on one side you have passed the regular expression and you haven’t passed the other, then the other side will get auto-generated.

Most often you will use that method together with the `regex` helper method. E.g. `consumer(regex('[0-9]{10}'))`.

To sum it up the contract for the aforementioned scenario would look more or less like this (the regular expression for time and UUID are simplified and most likely invalid but we want to keep things very simple in this example):

    org.springframework.cloud.contract.spec.Contract.make {
    				request {
    					method 'GET'
    					url '/someUrl'
    					body([
    					    time : value(consumer(regex('[0-9]{4}-[0-9]{2}-[0-9]{2} [0-2][0-9]-[0-5][0-9]-[0-5][0-9]')),
    					    id: value(consumer(regex('[0-9a-zA-z]{8}-[0-9a-zA-z]{4}-[0-9a-zA-z]{4}-[0-9a-zA-z]{12}'))
    					    body: "foo"
    					])
    				}
    			response {
    				status 200
    				body([
    					    time : value(producer(regex('[0-9]{4}-[0-9]{2}-[0-9]{2} [0-2][0-9]-[0-5][0-9]-[0-5][0-9]')),
    					    id: value([producer(regex('[0-9a-zA-z]{8}-[0-9a-zA-z]{4}-[0-9a-zA-z]{4}-[0-9a-zA-z]{12}'))
    					    body: "bar"
    					])
    			}
    }

Important | Please read the Groovy docs related to JSON to understand how to properly structure the request / response bodies.

#### How to do Stubs versioning?

##### API Versioning

Let’s try to answer a question what versioning really means. If you’re referring to the API version then there are different approaches.

- use Hypermedia, links and do not version your API by any means

- pass versions through headers / urls

I will not try to answer a question which approach is better. Whatever suit your needs and allows you to generate business value should be picked.

Let’s assume that you do version your API. In that case you should provide as many contracts as many versions you support. You can create a subfolder for every version or append it to th contract name - whatever suits you more.

##### JAR versioning

If by versioning you mean the version of the JAR that contains the stubs then there are essentially two main approaches.

Let’s assume that you’re doing Continuous Delivery / Deployment which means that you’re generating a new version of the jar each time you go through the pipeline and that jar can go to production at any time. For example your jar version looks like this (it got built on the 20.10.2016 at 20:15:21) :

    1.0.0.20161020-201521-RELEASE

In that case your generated stub jar will look like this.

    1.0.0.20161020-201521-RELEASE-stubs.jar

In this case you should inside your `application.yml` or `@AutoConfigureStubRunner` when referencing stubs provide the latest version of the stubs. You can do that by passing the `+` sign. Example

    @AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:stubs:8080"})

If the versioning however is fixed (e.g. `1.0.4.RELEASE` or `2.1.1`) then you have to set the concrete value of the jar version. Example for 2.1.1.

    @AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:2.1.1:stubs:8080"})

##### Dev or prod stubs

You can manipulate the classifier to run the tests against current development version of the stubs of other services or the ones that were deployed to production. If you alter your build to deploy the stubs with the `prod-stubs` classifier once you reach production deployment then you can run tests in one case with dev stubs and one with prod stubs.

Example of tests using development version of stubs

    @AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:stubs:8080"})

Example of tests using production version of stubs

    @AutoConfigureStubRunner(ids = {"com.example:http-server-dsl:+:prod-stubs:8080"})

You can pass those values also via properties from your deployment pipeline.

#### Common repo with contracts

Another way of storing contracts other than having them with the producer is keeping them in a common place. It can be related to security issues where the consumers can’t clone the producer’s code. Also if you keep contracts in a single place then you, as a producer, will know how many consumers you have and which consumer will you break with your local changes.

##### Repo structure

Let’s assume that we have a producer with coordinates `com.example:server` and 3 consumers: `client1`, `client2`, `client3`. Then in the repository with common contracts you would have the following setup (which you can checkout here:

    ├── com
    │   └── example
    │       └── server
    │           ├── client1
    │           │   └── expectation.groovy
    │           ├── client2
    │           │   └── expectation.groovy
    │           ├── client3
    │           │   └── expectation.groovy
    │           └── pom.xml
    ├── mvnw
    ├── mvnw.cmd
    ├── pom.xml
    └── src
        └── assembly
            └── contracts.xml

As you can see the under the slash-delimited groupid `/` artifact id folder (`com/example/server`) you have expectations of the 3 consumers (`client1`, `client2` and `client3`). Expectations are the standard Groovy DSL contract files as described throughout this documentation. This repository has to produce a JAR file that maps one to one to the contents of the repo.

Example of a `pom.xml` inside the `server` folder.

    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>

    	<groupId>com.example</groupId>
    	<artifactId>server</artifactId>
    	<version>0.0.1-SNAPSHOT</version>

    	<name>Server Stubs</name>
    	<description>POM used to install locally stubs for consumer side</description>

    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>1.4.2.BUILD-SNAPSHOT</version>
    		<relativePath />
    	</parent>

    	<properties>
    		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    		<java.version>1.8</java.version>
    		<spring-cloud-contract.version>1.0.4.BUILD-SNAPSHOT</spring-cloud-contract.version>
    		<spring-cloud-dependencies.version>Camden.BUILD-SNAPSHOT</spring-cloud-dependencies.version>
    		<excludeBuildFolders>true</excludeBuildFolders>
    	</properties>

    	<dependencyManagement>
    		<dependencies>
    			<dependency>
    				<groupId>org.springframework.cloud</groupId>
    				<artifactId>spring-cloud-dependencies</artifactId>
    				<version>${spring-cloud-dependencies.version}</version>
    				<type>pom</type>
    				<scope>import</scope>
    			</dependency>
    		</dependencies>
    	</dependencyManagement>

    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.springframework.cloud</groupId>
    				<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    				<version>${spring-cloud-contract.version}</version>
    				<extensions>true</extensions>
    				<configuration>
    					<!-- By default it would search under src/test/resources/ -->
    					<contractsDirectory>${project.basedir}</contractsDirectory>
    				</configuration>
    			</plugin>
    		</plugins>
    	</build>

    	<repositories>
    		<repository>
    			<id>spring-snapshots</id>
    			<name>Spring Snapshots</name>
    			<url>https://repo.spring.io/snapshot</url>
    			<snapshots>
    				<enabled>true</enabled>
    			</snapshots>
    		</repository>
    		<repository>
    			<id>spring-milestones</id>
    			<name>Spring Milestones</name>
    			<url>https://repo.spring.io/milestone</url>
    			<snapshots>
    				<enabled>false</enabled>
    			</snapshots>
    		</repository>
    		<repository>
    			<id>spring-releases</id>
    			<name>Spring Releases</name>
    			<url>https://repo.spring.io/release</url>
    			<snapshots>
    				<enabled>false</enabled>
    			</snapshots>
    		</repository>
    	</repositories>
    	<pluginRepositories>
    		<pluginRepository>
    			<id>spring-snapshots</id>
    			<name>Spring Snapshots</name>
    			<url>https://repo.spring.io/snapshot</url>
    			<snapshots>
    				<enabled>true</enabled>
    			</snapshots>
    		</pluginRepository>
    		<pluginRepository>
    			<id>spring-milestones</id>
    			<name>Spring Milestones</name>
    			<url>https://repo.spring.io/milestone</url>
    			<snapshots>
    				<enabled>false</enabled>
    			</snapshots>
    		</pluginRepository>
    		<pluginRepository>
    			<id>spring-releases</id>
    			<name>Spring Releases</name>
    			<url>https://repo.spring.io/release</url>
    			<snapshots>
    				<enabled>false</enabled>
    			</snapshots>
    		</pluginRepository>
    	</pluginRepositories>

    </project>

As you can see there are no dependencies other than the Spring Cloud Contract Maven Plugin. Those poms are necessary for the consumer side to run `mvn clean install -DskipTests` to locally install stubs of the producer project.

The `pom.xml` in the root folder can look like this:

    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>

    	<groupId>com.example.standalone</groupId>
    	<artifactId>contracts</artifactId>
    	<version>0.0.1-SNAPSHOT</version>

    	<name>Contracts</name>
    	<description>Contains all the Spring Cloud Contracts, well, contracts. JAR used by the producers to generate tests and stubs</description>

    	<properties>
    		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    	</properties>

    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.apache.maven.plugins</groupId>
    				<artifactId>maven-assembly-plugin</artifactId>
    				<executions>
    					<execution>
    						<id>contracts</id>
    						<phase>prepare-package</phase>
    						<goals>
    							<goal>single</goal>
    						</goals>
    						<configuration>
    							<attach>true</attach>
    							<descriptor>${basedir}/src/assembly/contracts.xml</descriptor>
    							<!-- If you want an explicit classifier remove the following line -->
    							<appendAssemblyId>false</appendAssemblyId>
    						</configuration>
    					</execution>
    				</executions>
    			</plugin>
    		</plugins>
    	</build>

    </project>

It’s using the assembly plugin in order to build the JAR with all the contracts. Example of such setup is here:

    <assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.3"
    		  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    		  xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.3 http://maven.apache.org/xsd/assembly-1.1.3.xsd">
    	<id>project</id>
    	<formats>
    		<format>jar</format>
    	</formats>
    	<includeBaseDirectory>false</includeBaseDirectory>
    	<fileSets>
    		<fileSet>
    			<directory>${project.basedir}</directory>
    			<outputDirectory>/</outputDirectory>
    			<useDefaultExcludes>true</useDefaultExcludes>
    			<excludes>
    				<exclude>**/${project.build.directory}/**</exclude>
    				<exclude>mvnw</exclude>
    				<exclude>mvnw.cmd</exclude>
    				<exclude>.mvn/**</exclude>
    				<exclude>src/**</exclude>
    			</excludes>
    		</fileSet>
    	</fileSets>
    </assembly>

##### Workflow

The workflow would look similar to the one presented in the `Step by step guide to CDC`. The only difference is that the producer doesn’t own the contracts anymore. So the consumer and the producer have to work on common contracts in a common repository.

###### Consumer

When the consumer wants to work on the contracts offline, instead of cloning the producer code, the consumer team clones the common repository, goes to the required producer’s folder (e.g. `com/example/server`) and runs `mvn clean install -DskipTests` to install locally the stubs converted from the contracts.

Tip | You need to have Maven installed locally

###### Producer

As a producer it’s enough to alter the Spring Cloud Contract Verifier to provide the URL and the dependency of the JAR containing the contracts:

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<configuration>
    		<contractsRepositoryUrl>http://link/to/your/nexus/or/artifactory/or/sth</contractsRepositoryUrl>
    		<contractDependency>
    			<groupId>com.example.standalone</groupId>
    			<artifactId>contracts</artifactId>
    		</contractDependency>
    	</configuration>
    </plugin>

With this setup the JAR with groupid `com.example.standalone` and artifactid `contracts` will be downloaded from `http://link/to/your/nexus/or/artifactory/or/sth`. It will be then unpacked in a local temporary folder and contracts present under the `com/example/server` will be picked as the ones used to generate the tests and the stubs. Due to this convention the producer team will know which consumer teams will be broken when some incompatible changes are done.

The rest of the flow looks the same.

#### Can I have multiple base classes for tests?

Yes! Check out the Different base classes for contracts sections of either Gradle or Maven plugins.

### Spring Cloud Contract Verifier HTTP

#### Gradle Project

##### Prerequisites

In order to use Spring Cloud Contract Verifier with WireMock you have to use Gradle or Maven plugin.

Warning | If you want to use Spock in your projects you have to add separately the `spock-core` and `spock-spring` modules. Check Spock docs for more information

###### Add gradle plugin with dependencies

    buildscript {
    	repositories {
    		mavenCentral()
    	}
    	dependencies {
    	    classpath "org.springframework.boot:spring-boot-gradle-plugin:${springboot_version}"
    		classpath "org.springframework.cloud:spring-cloud-contract-gradle-plugin:${verifier_version}"
    	}
    }

    apply plugin: 'groovy'
    apply plugin: 'spring-cloud-contract'

    dependencyManagement {
    	imports {
    		mavenBom "org.springframework.cloud:spring-cloud-contract-dependencies:${verifier_version}"
    	}
    }

    dependencies {
    	testCompile 'org.codehaus.groovy:groovy-all:2.4.6'
    	// example with adding Spock core and Spock Spring
    	testCompile 'org.spockframework:spock-core:1.0-groovy-2.4'
    	testCompile 'org.spockframework:spock-spring:1.0-groovy-2.4'
    	testCompile 'org.springframework.cloud:spring-cloud-starter-contract-verifier'
    }

###### Snapshot versions for Gradle

Add the additional snapshot repository to your build.gradle to use snapshot versions which are automatically uploaded after every successful build:

    buildscript {
    	repositories {
    		mavenCentral()
    		mavenLocal()
    		maven { url "http://repo.spring.io/snapshot" }
    		maven { url "http://repo.spring.io/milestone" }
    		maven { url "http://repo.spring.io/release" }
    	}
    }

###### Add stubs

By default Spring Cloud Contract Verifier is looking for stubs in `src/test/resources/contracts` directory.

Directory containing stub definitions is treated as a class name, and each stub definition is treated as a single test. We assume that it contains at least one directory which will be used as test class name. If there is more than one level of nested directories all except the last one will be used as package name. So with following structure

    src/test/resources/contracts/myservice/shouldCreateUser.groovy
    src/test/resources/contracts/myservice/shouldReturnUser.groovy

Spring Cloud Contract Verifier will create test class `defaultBasePackage.MyService` with two methods

- `shouldCreateUser()`

- `shouldReturnUser()`

##### Run plugin

Plugin registers itself to be invoked before `check` task. You have nothing to do as long as you want it to be part of your build process. If you just want to generate tests please invoke `generateContractTests` task.

##### Default setup

Default Gradle Plugin setup creates the following Gradle part of the build (it’s a pseudocode)

    contracts {
        targetFramework = 'JUNIT'
        testMode = 'MockMvc'
        generatedTestSourcesDir = project.file("${project.buildDir}/generated-test-sources/contracts")
        contractsDslDir = "${project.rootDir}/src/test/resources/contracts"
        basePackageForTests = 'org.springframework.cloud.verifier.tests'
        stubsOutputDir = project.file("${project.buildDir}/stubs")

        // the following properties are used when you want to provide where the JAR with contract lays
        contractDependency {
            stringNotation = ''
        }
        contractsPath = ''
        contractsWorkOffline = false
    }

    tasks.create(type: Jar, name: 'verifierStubsJar', dependsOn: 'generateWireMockClientStubs') {
        baseName = project.name
        classifier = contracts.stubsSuffix
        from contractVerifier.stubsOutputDir
    }

    project.artifacts {
        archives task
    }

    tasks.create(type: Copy, name: 'copyContracts') {
        from contracts.contractsDslDir
        into contracts.stubsOutputDir
    }

    verifierStubsJar.dependsOn 'copyContracts'

    publishing {
        publications {
            stubs(MavenPublication) {
                artifactId project.name
                artifact verifierStubsJar
            }
        }
    }

##### Configure plugin

To change default configuration just add `contracts` snippet to your Gradle config

    contracts {
    	testMode = 'MockMvc'
    	baseClassForTests = 'org.mycompany.tests'
    	generatedTestSourcesDir = project.file('src/generatedContract')
    }

###### Configuration options

- testMode - defines mode for acceptance tests. By default MockMvc which is based on Spring’s MockMvc. It can also be changed to JaxRsClient or to Explicit for real HTTP calls.

- imports - array with imports that should be included in generated tests (for example ['org.myorg.Matchers']). By default empty array []

- staticImports - array with static imports that should be included in generated tests(for example ['org.myorg.Matchers.*']). By default empty array []

- basePackageForTests - specifies base package for all generated tests. By default set to org.springframework.cloud.verifier.tests

- baseClassForTests - base class for all generated tests. By default `spock.lang.Specification` if using Spock tests.

- packageWithBaseClasses - instead of providing a fixed value for base class you can provide a package where all the base classes lay. Takes precedence over baseClassForTests.

- baseClassMappings - explicitly map contract package to a FQN of a base class. Takes precedence over packageWithBaseClasses and baseClassForTests.

- ruleClassForTests - specifies Rule which should be added to generated test classes.

- ignoredFiles - Ant matcher allowing defining stub files for which processing should be skipped. By default empty array []

- contractsDslDir - directory containing contracts written using the GroovyDSL. By default `$rootDir/src/test/resources/contracts`

- generatedTestSourcesDir - test source directory where tests generated from Groovy DSL should be placed. By default `$buildDir/generated-test-sources/contractVerifier`

- stubsOutputDir - dir where the generated WireMock stubs from Groovy DSL should be placed

- targetFramework - the target test framework to be used; currently Spock and JUnit are supported with JUnit being the default framework

The following properties are used when you want to provide where the JAR with contract lays

- contractDependency - the Dependency that provides `groupid:artifactid:version:classifier` coordinates. You can use the `contractDependency` closure to set it up

- contractsPath - if contract deps are downloaded will default to `groupid/artifactid` where `groupid` will be slash separated. Otherwise will scan contracts under provided directory

- contractsWorkOffline - in order not to download the dependencies each time you can download them once and work offline afterwards (reuse local Maven repo)

###### Single base class for all tests

When using Spring Cloud Contract Verifier in default MockMvc you need to create a base specification for all generated acceptance tests. In this class you need to point to endpoint which should be verified.

    abstract class BaseMockMvcSpec extends Specification {

    	def setup() {
    		RestAssuredMockMvc.standaloneSetup(new PairIdController())
    	}

    	void isProperCorrelationId(Integer correlationId) {
    		assert correlationId == 123456
    	}

    	void isEmpty(String value) {
    		assert value == null
    	}

    }

In case of using `Explicit` mode, you can use base class to initialize the whole tested app similarly as in regular integration tests. In case of `JAXRSCLIENT` mode this base class should also contain `protected WebTarget webTarget` field, right now the only option to test JAX-RS API is to start a web server.

###### Different base classes for contracts

If your base classes differ between contracts you can tell the Spring Cloud Contract plugin which class should get extended by the autogenerated tests. You have two options:

- follow a convention by providing the `packageWithBaseClasses`

- provide explicit mapping via `baseClassMappings`

Convention

The convention is such that if you have a contract under e.g. `src/test/resources/contract/foo/bar/baz/` and provide the value of the `packageWithBaseClasses` property to `com.example.base` then we will assume that there is a `BarBazBase` class under `com.example.base` package. In other words we take last two parts of package if they exist and form a class with a `Base` suffix. Takes precedence over baseClassForTests. Example of usage in the `contracts` closure:

    packageWithBaseClasses = 'com.example.base'

Mapping

You can manually map a regular expression of the contract’s package to fully qualified name of the base class for the matched contract. Let’s take a look at the following example:

    baseClassForTests = "com.example.FooBase"
    baseClassMappings {
    	baseClassMapping('.*/com/.*', 'com.example.ComBase')
    	baseClassMapping('.*/bar/.*':'com.example.BarBase')
    }

Let’s assume that you have contracts under - `src/test/resources/contract/com/` - `src/test/resources/contract/foo/`

By providing the `baseClassForTests` we have a fallback in case mapping didn’t succeed (you could also provide the `packageWithBaseClasses` as fallback). That way the tests generated from `src/test/resources/contract/com/` contracts will be extending the `com.example.ComBase` whereas the rest of tests will extend `com.example.FooBase`.

##### Invoking generated tests

To ensure that provider side is complaint with defined contracts, you need to invoke:

    ./gradlew generateContractTests test

##### Spring Cloud Contract Verifier on consumer side

In consumer service you need to configure Spring Cloud Contract Verifier plugin in exactly the same way as in case of provider. If you don’t want to use Stub Runner then you need to copy contracts stored in `src/test/resources/contracts` and generate WireMock json stubs using:

    ./gradlew generateWireMockClientStubs

Note that `stubsOutputDir` option has to be set for stub generation to work.

When present, json stubs can be used in consumer automated tests.

    @ContextConfiguration(loader == SpringApplicationContextLoader, classes == Application)
    class LoanApplicationServiceSpec extends Specification {

     @ClassRule
     @Shared
     WireMockClassRule wireMockRule == new WireMockClassRule()

     @Autowired
     LoanApplicationService sut

     def 'should successfully apply for loan'() {
       given:
     	LoanApplication application =
    			new LoanApplication(client: new Client(clientPesel: '12345678901'), amount: 123.123)
       when:
    	LoanApplicationResult loanApplication == sut.loanApplication(application)
       then:
    	loanApplication.loanApplicationStatus == LoanApplicationStatus.LOAN_APPLIED
    	loanApplication.rejectionReason == null
     }
    }

Underneath LoanApplication makes a call to FraudDetection service. This request is handled by WireMock server configured using stubs generated by Spring Cloud Contract Verifier.

#### Using in your Maven project

##### Add maven plugin

Add the Spring Cloud Contract BOM

    <dependencyManagement>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-dependencies</artifactId>
    			<version>${spring-cloud-dependencies.version}</version>
    			<type>pom</type>
    			<scope>import</scope>
    		</dependency>
    	</dependencies>
    </dependencyManagement>

Next, the `Spring Cloud Contract Verifier` Maven plugin

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<version>${spring-cloud-contract.version}</version>
    	<extensions>true</extensions>
    	<configuration>
    		<packageWithBaseClasses>com.example.fraud</packageWithBaseClasses>
    	</configuration>
    </plugin>

You can read more in the Spring Cloud Contract Maven Plugin Docs

###### Snapshot versions for Maven

For Snapshot / Milestone versions you have to add the following section to your `pom.xml`

    <repositories>
    	<repository>
    		<id>spring-snapshots</id>
    		<name>Spring Snapshots</name>
    		<url>https://repo.spring.io/snapshot</url>
    		<snapshots>
    			<enabled>true</enabled>
    		</snapshots>
    	</repository>
    	<repository>
    		<id>spring-milestones</id>
    		<name>Spring Milestones</name>
    		<url>https://repo.spring.io/milestone</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</repository>
    	<repository>
    		<id>spring-releases</id>
    		<name>Spring Releases</name>
    		<url>https://repo.spring.io/release</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</repository>
    </repositories>
    <pluginRepositories>
    	<pluginRepository>
    		<id>spring-snapshots</id>
    		<name>Spring Snapshots</name>
    		<url>https://repo.spring.io/snapshot</url>
    		<snapshots>
    			<enabled>true</enabled>
    		</snapshots>
    	</pluginRepository>
    	<pluginRepository>
    		<id>spring-milestones</id>
    		<name>Spring Milestones</name>
    		<url>https://repo.spring.io/milestone</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</pluginRepository>
    	<pluginRepository>
    		<id>spring-releases</id>
    		<name>Spring Releases</name>
    		<url>https://repo.spring.io/release</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</pluginRepository>
    </pluginRepositories>

##### Add stubs

By default Spring Cloud Contract Verifier is looking for stubs in `src/test/resources/contracts` directory. Directory containing stub definitions is treated as a class name, and each stub definition is treated as a single test. We assume that it contains at least one directory which will be used as test class name. If there is more than one level of nested directories all except the last one will be used as package name. So with following structure

    src/test/resources/contracts/myservice/shouldCreateUser.groovy
    src/test/resources/contracts/myservice/shouldReturnUser.groovy

Spring Cloud Contract Verifier will create test class `defaultBasePackage.MyService` with two methods - `shouldCreateUser()` - `shouldReturnUser()`

##### Run plugin

Plugin goal `generateTests` is assigned to be invoked in phase `generate-test-sources`. You have nothing to do as long as you want it to be part of your build process. If you just want to generate tests please invoke `generateTests` goal.

##### Configure plugin

To change default configuration just add `configuration` section to plugin definition or `execution` definition.

    <plugin>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-contract-maven-plugin</artifactId>
        <executions>
            <execution>
                <goals>
                    <goal>convert</goal>
                    <goal>generateStubs</goal>
                    <goal>generateTests</goal>
                </goals>
            </execution>
        </executions>
        <configuration>
            <basePackageForTests>org.springframework.cloud.verifier.twitter.place</basePackageForTests>
            <baseClassForTests>org.springframework.cloud.verifier.twitter.place.BaseMockMvcSpec</baseClassForTests>
        </configuration>
    </plugin>

###### Important configuration options

- testMode - defines mode for acceptance tests. By default `MockMvc` which is based on Spring’s MockMvc. It can also be changed to `JaxRsClient` or to `Explicit` for real HTTP calls.

- basePackageForTests - specifies base package for all generated tests. By default set to `org.springframework.cloud.verifier.tests`.

- ruleClassForTests - specifies Rule which should be added to generated test classes.

- baseClassForTests - base class for generated tests. By default `spock.lang.Specification` if using Spock tests.

- contractsDir - directory containing contracts written using the GroovyDSL. By default `/src/test/resources/contracts`.

- testFramework - the target test framework to be used; currently Spock and JUnit are supported with JUnit being the default framework

- packageWithBaseClasses - instead of providing a fixed value for base class you can provide a package where all the base classes lay. The convention is such that if you have a contract under `src/test/resources/contract/foo/bar/baz/` and provide the value of this property to `com.example.base` then we will assume that there is a `BarBazBase` class under `com.example.base` package. Takes precedence over baseClassForTests

- baseClassMappings - list of base class mappings that where you have to provide `contractPackageRegex` which is checked against the package in which the contract lays and `baseClassFQN` that maps to fully qualified name of the base class for the matched contract. If you have a contract under `src/test/resources/contract/foo/bar/baz/` and map the property `.*` → `com.example.base.BaseClass` then the test class generated from these contracts will extend `com.example.base.BaseClass`. Takes precedence over packageWithBaseClasses and baseClassForTests.

If you want to download your contract definitions from a Maven repository you can use

- contractsRepositoryUrl - URL to a repo with the artifacts with contracts, if not provided should use the current Maven ones

- contractDependency - the contract dependency that contains all the packaged contracts

- contractsPath - path to concrete contracts in the JAR with packaged contracts. Defaults to `groupid/artifactid` where `gropuid` is slash separated.

- contractsWorkOffline - if the dependencies should be downloaded or local Maven only should be reused

For complete information take a look at Plugin Documentation

###### Single base class for all tests

When using Spring Cloud Contract Verifier in default MockMvc you need to create a base specification for all generated acceptance tests. In this class you need to point to endpoint which should be verified.

    package org.mycompany.tests

    import org.mycompany.ExampleSpringController
    import com.jayway.restassured.module.mockmvc.RestAssuredMockMvc
    import spock.lang.Specification

    class  MvcSpec extends Specification {
      def setup() {
       RestAssuredMockMvc.standaloneSetup(new ExampleSpringController())
      }
    }

In case of using `Explicit` mode, you can use base class to initialize the whole tested app similarly as in regular integration tests. In case of `JAXRSCLIENT` mode this base class should also contain `protected WebTarget webTarget` field, right now the only option to test JAX-RS API is to start a web server.

###### Different base classes for contracts

If your base classes differ between contracts you can tell the Spring Cloud Contract plugin which class should get extended by the autogenerated tests. You have two options:

- follow a convention by providing the `packageWithBaseClasses`

- provide explicit mapping via `baseClassMappings`

Convention

The convention is such that if you have a contract under e.g. `src/test/resources/contract/hello/v1/` and provide the value of the `packageWithBaseClasses` property to `hello` then we will assume that there is a `HelloV1Base` class under `hello` package. In other words we take last two parts of package if they exist and form a class with a `Base` suffix. Takes precedence over baseClassForTests. Example of usage:

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<configuration>
    		<packageWithBaseClasses>hello</packageWithBaseClasses>
    	</configuration>
    </plugin>

Mapping

You can manually map a regular expression of the contract’s package to fully qualified name of the base class for the matched contract. You have to provide a list `baseClassMappings` of `baseClassMapping` that takes a `contractPackageRegex` to `baseClassFQN` mapping. Let’s take a look at the following example:

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<configuration>
    		<baseClassForTests>com.example.FooBase</baseClassForTests>
    		<baseClassMappings>
    			<baseClassMapping>
    				<contractPackageRegex>.*com.*</contractPackageRegex>
    				<baseClassFQN>com.example.TestBase</baseClassFQN>
    			</baseClassMapping>
    		</baseClassMappings>
    	</configuration>
    </plugin>

Let’s assume that you have contracts under - `src/test/resources/contract/com/` - `src/test/resources/contract/foo/`

By providing the `baseClassForTests` we have a fallback in case mapping didn’t succeed (you could also provide the `packageWithBaseClasses` as fallback). That way the tests generated from `src/test/resources/contract/com/` contracts will be extending the `com.example.ComBase` whereas the rest of tests will extend `com.example.FooBase`.

##### Invoking generated tests

Spring Cloud Contract Maven Plugin generates verification code into directory `/generated-test-sources/contractVerifier` and attach this directory to `testCompile` goal.

For Groovy Spock code use:

    <plugin>
    	<groupId>org.codehaus.gmavenplus</groupId>
    	<artifactId>gmavenplus-plugin</artifactId>
    	<version>1.5</version>
    	<executions>
    		<execution>
    			<goals>
    				<goal>testCompile</goal>
    			</goals>
    		</execution>
    	</executions>
    	<configuration>
    		<testSources>
    			<testSource>
    				<directory>${project.basedir}/src/test/groovy</directory>
    				<includes>
    					<include>**/*.groovy</include>
    				</includes>
    			</testSource>
    			<testSource>
    				<directory>${project.build.directory}/generated-test-sources/contractVerifier</directory>
    				<includes>
    					<include>**/*.groovy</include>
    				</includes>
    			</testSource>
    		</testSources>
    	</configuration>
    </plugin>

To ensure that provider side is complaint with defined contracts, you need to invoke `mvn generateTest test`

##### FAQ with Maven Plugin

###### Maven Plugin and STS

In case you see the following exception while using STS

when you click on the marker you should see sth like this

     plugin:1.1.0.M1:convert:default-convert:process-test-resources) org.apache.maven.plugin.PluginExecutionException: Execution default-convert of goal org.springframework.cloud:spring-
     cloud-contract-maven-plugin:1.1.0.M1:convert failed. at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145) at
     org.eclipse.m2e.core.internal.embedder.MavenImpl.execute(MavenImpl.java:331) at org.eclipse.m2e.core.internal.embedder.MavenImpl$11.call(MavenImpl.java:1362) at
    ...
     org.eclipse.core.internal.jobs.Worker.run(Worker.java:55) Caused by: java.lang.NullPointerException at
     org.eclipse.m2e.core.internal.builder.plexusbuildapi.EclipseIncrementalBuildContext.hasDelta(EclipseIncrementalBuildContext.java:53) at
     org.sonatype.plexus.build.incremental.ThreadBuildContext.hasDelta(ThreadBuildContext.java:59) at

In order to fix this issue just provide the following section in your `pom.xml`

    <build>
        <pluginManagement>
            <plugins>
                <!--This plugin's configuration is used to store Eclipse m2e settings
                    only. It has no influence on the Maven build itself. -->
                <plugin>
                    <groupId>org.eclipse.m2e</groupId>
                    <artifactId>lifecycle-mapping</artifactId>
                    <version>1.0.0</version>
                    <configuration>
                        <lifecycleMappingMetadata>
                            <pluginExecutions>
                                 <pluginExecution>
                                    <pluginExecutionFilter>
                                        <groupId>org.springframework.cloud</groupId>
                                        <artifactId>spring-cloud-contract-maven-plugin</artifactId>
                                        <versionRange>[1.0,)</versionRange>
                                        <goals>
                                            <goal>convert</goal>
                                        </goals>
                                    </pluginExecutionFilter>
                                    <action>
                                        <execute />
                                    </action>
                                 </pluginExecution>
                            </pluginExecutions>
                        </lifecycleMappingMetadata>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>

##### Spring Cloud Contract Verifier on consumer side

You can actually use the Spring Cloud Contract Verifier also for the consumer side! You can use the plugin so that it only converts the contracts and generates the stubs. To achieve that you need to configure Spring Cloud Contract Verifier plugin in exactly the same way as in case of provider. You need to copy contracts stored in `src/test/resources/contracts` and generate WireMock json stubs using: `mvn generateStubs` command. By default generated WireMock mapping is stored in directory `target/mappings`. Your project should create from this generated mappings additional artifact with classifier `stubs` for easy deploy to maven repository.

Sample configuration:

    <plugin>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-contract-maven-plugin</artifactId>
        <version>${verifier-plugin.version}</version>
        <executions>
            <execution>
                <goals>
                    <goal>convert</goal>
                    <goal>generateStubs</goal>
                </goals>
            </execution>
        </executions>
    </plugin>

When present, json stubs can be used in consumer automated tests.

    @RunWith(SpringTestRunner.class)
    @SpringBootTest
    @AutoConfigureStubRunner
    public class LoanApplicationServiceTests {

      @Autowired
      LoanApplicationService service;

      @Test
      public void shouldSuccessfullyApplyForLoan() {
        //given:
     	LoanApplication application =
    			new LoanApplication(new Client("12345678901"), 123.123);
        //when:
    	LoanApplicationResult loanApplication = service.loanApplication(application);
        // then:
    	assertThat(loanApplication.loanApplicationStatus).isEqualTo(LoanApplicationStatus.LOAN_APPLIED);
    	assertThat(loanApplication.rejectionReason).isNull();
      }
    }

Underneath `LoanApplication` makes a call to the `FraudDetection` service. This request is handled by a WireMock server configured using stubs generated by Spring Cloud Contract Verifier.

#### Scenarios

It’s possible to handle scenarios with Spring Cloud Contract Verifier. All you need to do is to stick to proper naming convention while creating your contracts. The convention requires to include order number followed by the underscore.

    my_contracts_dir\
      scenario1\
        1_login.groovy
        2_showCart.groovy
        3_logout.groovy

Such tree will cause Spring Cloud Contract Verifier generating WireMock’s scenario with name `scenario1` and three steps:

- login marked as `Started` pointing to:

- showCart marked as `Step1` pointing to:

- logout marked as `Step2` which will close the scenario.

More details about WireMock scenarios can be found under http://wiremock.org/stateful-behaviour.html

Spring Cloud Contract Verifier will also generate tests with guaranteed order of execution.

#### Stubs and transitive dependencies

The Maven and Gradle plugin that we’re created are adding the tasks that create the stubs jar for you. What can be problematic is that when reusing the stubs you can by mistake import all of that stub dependencies! When building a Maven artifact even though you have a couple of different jars, all of them share one pom:

    ├── github-webhook-0.0.1.BUILD-20160903.075506-1-stubs.jar
    ├── github-webhook-0.0.1.BUILD-20160903.075506-1-stubs.jar.sha1
    ├── github-webhook-0.0.1.BUILD-20160903.075655-2-stubs.jar
    ├── github-webhook-0.0.1.BUILD-20160903.075655-2-stubs.jar.sha1
    ├── github-webhook-0.0.1.BUILD-SNAPSHOT.jar
    ├── github-webhook-0.0.1.BUILD-SNAPSHOT.pom
    ├── github-webhook-0.0.1.BUILD-SNAPSHOT-stubs.jar
    ├── ...
    └── ...

There are three possibilities of working with those dependencies so as not to have any issues with transitive dependencies.

Mark all application dependencies as optional

If in the `github-webhook` application we would mark all of our dependencies as optional, when you include the `github-webhook` stubs in another application (or when that dependency gets downloaded by Stub Runner) then, since all of the depenencies are optional, they will not get downloaded.

Create a separate artifactid for stubs

If you create a separate artifactid then you can set it up in whatever way you wish. For example by having no dependencies at all.

Exclude dependencies on the consumer side

As a consumer, if you add the stub dependency to your classpath you can explicitly exclude the unwanted dependencies.

### Spring Cloud Contract Verifier Messaging

Spring Cloud Contract Verifier allows you to verify your application that uses messaging as means of communication. All of our integrations are working with Spring but you can also create one yourself and use it.

#### Integrations

You can use one of the four integration configurations:

- Apache Camel

- Spring Integration

- Spring Cloud Stream

- Spring AMQP

Since we’re using Spring Boot then if you have added one of the aforementioned libraries to the classpath then automatically all the messaging configuration will be set up.

Important | Remember to put `@AutoConfigureMessageVerifier` on the base class of your generated tests. Otherwise messaging part of Spring Cloud Contract Verifier will not work.

#### Manual Integration Testing

The main interface used by the tests is the `org.springframework.cloud.contract.verifier.messaging.MessageVerifier`. It defines how to send and receive messages. You can create your own implementation to achieve the same goal.

In the a test you can inject a `ContractVerifierMessageExchange` to send and receive messages that follow the contract. Then add `@AutoConfigureMessageVerifier` to your test, e.g.

    @RunWith(SpringTestRunner.class)
    @SpringBootTest
    @AutoConfigureMessageVerifier
    public static class MessagingContractTests {

      @Autowired
      private MessageVerifier verifier;
      ...
    }

Note | If your tests require stubs as well, then `@AutoConfigureStubRunner` includes the messaging configuration, so you only need the one annotation.

#### Publisher side test generation

Having the `input` or `outputMessage` sections in your DSL will result in creation of tests on the publisher’s side. By default JUnit tests will be created, however there is also a possibility to create Spock tests.

There are 3 main scenarios that we should take into consideration:

- Scenario 1: there is no input message that produces an output one. The output message is triggered by a component inside the application (e.g. scheduler)

- Scenario 2: the input message triggers an output message

- Scenario 3: the input message is consumed and there is no output message

##### Scenario 1 (no input message)

For the given contract:

    def contractDsl = Contract.make {
    	label 'some_label'
    	input {
    		triggeredBy('bookReturnedTriggered()')
    	}
    	outputMessage {
    		sentTo('activemq:output')
    		body('''{ "bookName" : "foo" }''')
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

The following JUnit test will be created:

    '''
     // when:
      bookReturnedTriggered();

     // then:
      ContractVerifierMessage response = contractVerifierMessaging.receive("activemq:output");
      assertThat(response).isNotNull();
      assertThat(response.getHeader("BOOK-NAME")).isEqualTo("foo");
     // and:
      DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.getPayload()));
      assertThatJson(parsedJson).field("bookName").isEqualTo("foo");
    '''

And the following Spock test would be created:

    '''
     when:
      bookReturnedTriggered()

     then:
      ContractVerifierMessage response = contractVerifierMessaging.receive('activemq:output')
      assert response != null
      response.getHeader('BOOK-NAME')  == 'foo'
     and:
      DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.payload))
      assertThatJson(parsedJson).field("bookName").isEqualTo("foo")

    '''

##### Scenario 2 (output triggered by input)

For the given contract:

    def contractDsl = Contract.make {
    	label 'some_label'
    	input {
    		messageFrom('jms:input')
    		messageBody([
    				bookName: 'foo'
    		])
    		messageHeaders {
    			header('sample', 'header')
    		}
    	}
    	outputMessage {
    		sentTo('jms:output')
    		body([
    				bookName: 'foo'
    		])
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

The following JUnit test will be created:

    '''
    // given:
     ContractVerifierMessage inputMessage = contractVerifierMessaging.create(
      "{\\"bookName\\":\\"foo\\"}"
    , headers()
      .header("sample", "header"));

    // when:
     contractVerifierMessaging.send(inputMessage, "jms:input");

    // then:
     ContractVerifierMessage response = contractVerifierMessaging.receive("jms:output");
     assertThat(response).isNotNull();
     assertThat(response.getHeader("BOOK-NAME")).isEqualTo("foo");
    // and:
     DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.getPayload()));
     assertThatJson(parsedJson).field("bookName").isEqualTo("foo");
    '''

And the following Spock test would be created:

    """\
    given:
       ContractVerifierMessage inputMessage = contractVerifierMessaging.create(
        '''{"bookName":"foo"}''',
        ['sample': 'header']
      )

    when:
       contractVerifierMessaging.send(inputMessage, 'jms:input')

    then:
       ContractVerifierMessage response = contractVerifierMessaging.receive('jms:output')
       assert response !- null
       response.getHeader('BOOK-NAME')  == 'foo'
    and:
       DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.payload))
       assertThatJson(parsedJson).field("bookName").isEqualTo("foo")
    """

##### Scenario 3 (no output message)

For the given contract:

    def contractDsl = Contract.make {
    	label 'some_label'
    	input {
    		messageFrom('jms:delete')
    		messageBody([
    				bookName: 'foo'
    		])
    		messageHeaders {
    			header('sample', 'header')
    		}
    		assertThat('bookWasDeleted()')
    	}
    }

The following JUnit test will be created:

    '''
    // given:
     ContractVerifierMessage inputMessage = contractVerifierMessaging.create(
    	"{\\"bookName\\":\\"foo\\"}"
    , headers()
    	.header("sample", "header"));

    // when:
     contractVerifierMessaging.send(inputMessage, "jms:delete");

    // then:
     bookWasDeleted();
    '''

And the following Spock test would be created:

    '''
    given:
    	 ContractVerifierMessage inputMessage = contractVerifierMessaging.create(
    		\'\'\'{"bookName":"foo"}\'\'\',
    		['sample': 'header']
    	)

    when:
    	 contractVerifierMessaging.send(inputMessage, 'jms:delete')

    then:
    	 noExceptionThrown()
    	 bookWasDeleted()
    '''

#### Consumer Stub Side generation

Unlike the HTTP part - in Messaging we need to publish the Groovy DSL inside the JAR with a stub. Then it’s parsed on the consumer side and proper stubbed routes are created.

For more information please consult the Stub Runner Messaging sections.

Maven

    <dependencies>
    	<dependency>
    		<groupId>org.springframework.cloud</groupId>
    		<artifactId>spring-cloud-starter-stream-rabbit</artifactId>
    	</dependency>

    	<dependency>
    		<groupId>org.springframework.cloud</groupId>
    		<artifactId>spring-cloud-starter-contract-stub-runner</artifactId>
    		<scope>test</scope>
    	</dependency>
    	<dependency>
    		<groupId>org.springframework.cloud</groupId>
    		<artifactId>spring-cloud-stream-test-support</artifactId>
    		<scope>test</scope>
    	</dependency>
    </dependencies>

    <dependencyManagement>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-dependencies</artifactId>
    			<version>Camden.BUILD-SNAPSHOT</version>
    			<type>pom</type>
    			<scope>import</scope>
    		</dependency>
    	</dependencies>
    </dependencyManagement>

Gradle

    ext {
    	contractsDir = file("mappings")
    	stubsOutputDirRoot = file("${project.buildDir}/production/${project.name}-stubs/")
    }

    // Automatically added by plugin:
    // copyContracts - copies contracts to the output folder from which JAR will be created
    // verifierStubsJar - JAR with a provided stub suffix
    // the presented publication is also added by the plugin but you can modify it as you wish

    publishing {
    	publications {
    		stubs(MavenPublication) {
    			artifactId "${project.name}-stubs"
    			artifact verifierStubsJar
    		}
    	}
    }

### Spring Cloud Contract Stub Runner

One of the issues that you could have encountered while using Spring Cloud Contract Verifier was to pass the generated WireMock JSON stubs from the server side to the client side (or various clients). The same takes place in terms of client side generation for messaging.

Copying the JSON files / setting the client side for messaging manually is out of the question.

That’s why we’ll introduce Spring Cloud Contract Stub Runner that can download and run the stubs automatically for you.

#### Snapshot versions

Add the additional snapshot repository to your build.gradle to use snapshot versions which are automatically uploaded after every successful build:

Maven

    <repositories>
    	<repository>
    		<id>spring-snapshots</id>
    		<name>Spring Snapshots</name>
    		<url>https://repo.spring.io/snapshot</url>
    		<snapshots>
    			<enabled>true</enabled>
    		</snapshots>
    	</repository>
    	<repository>
    		<id>spring-milestones</id>
    		<name>Spring Milestones</name>
    		<url>https://repo.spring.io/milestone</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</repository>
    	<repository>
    		<id>spring-releases</id>
    		<name>Spring Releases</name>
    		<url>https://repo.spring.io/release</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</repository>
    </repositories>
    <pluginRepositories>
    	<pluginRepository>
    		<id>spring-snapshots</id>
    		<name>Spring Snapshots</name>
    		<url>https://repo.spring.io/snapshot</url>
    		<snapshots>
    			<enabled>true</enabled>
    		</snapshots>
    	</pluginRepository>
    	<pluginRepository>
    		<id>spring-milestones</id>
    		<name>Spring Milestones</name>
    		<url>https://repo.spring.io/milestone</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</pluginRepository>
    	<pluginRepository>
    		<id>spring-releases</id>
    		<name>Spring Releases</name>
    		<url>https://repo.spring.io/release</url>
    		<snapshots>
    			<enabled>false</enabled>
    		</snapshots>
    	</pluginRepository>
    </pluginRepositories>

Gradle

    buildscript {
    	repositories {
    		mavenCentral()
    		mavenLocal()
    		maven { url "http://repo.spring.io/snapshot" }
    		maven { url "http://repo.spring.io/milestone" }
    		maven { url "http://repo.spring.io/release" }
    	}

#### Publishing stubs as JARs

The easiest approach would be to centralize the way stubs are kept. For example you can keep them as JARs in a Maven repository.

Tip | For both Maven and Gradle the setup comes out of the box. But you can customize it if you want to.

Maven

    <!-- First disable the default jar setup in the properties section-->
    <!-- we don't want the verifier to do a jar for us -->
    <spring.cloud.contract.verifier.skip>true</spring.cloud.contract.verifier.skip>

    <!-- Next add the assembly plugin to your build -->
    <plugin>
    	<groupId>org.apache.maven.plugins</groupId>
    	<artifactId>maven-assembly-plugin</artifactId>
    	<executions>
    		<execution>
    			<id>stub</id>
    			<phase>prepare-package</phase>
    			<goals>
    				<goal>single</goal>
    			</goals>
    			<inherited>false</inherited>
    			<configuration>
    				<attach>true</attach>
    				<descriptor>${basedir}/src/assembly/stub.xml</descriptor>
    			</configuration>
    		</execution>
    	</executions>
    </plugin>

    <!-- Finally setup your assembly. Below you can find the contents of src/main/assembly/stub.xml -->
    <assembly
    	xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.3"
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.3 http://maven.apache.org/xsd/assembly-1.1.3.xsd">
    	<id>stubs</id>
    	<formats>
    		<format>jar</format>
    	</formats>
    	<includeBaseDirectory>false</includeBaseDirectory>
    	<fileSets>
    		<fileSet>
    			<directory>src/main/java</directory>
    			<outputDirectory>/</outputDirectory>
    			<includes>
    				<include>**com/example/model/*.*</include>
    			</includes>
    		</fileSet>
    		<fileSet>
    			<directory>${project.build.directory}/classes</directory>
    			<outputDirectory>/</outputDirectory>
    			<includes>
    				<include>**com/example/model/*.*</include>
    			</includes>
    		</fileSet>
    		<fileSet>
    			<directory>${project.build.directory}/snippets/stubs</directory>
    			<outputDirectory>META-INF/${project.groupId}/${project.artifactId}/${project.version}/mappings</outputDirectory>
    			<includes>
    				<include>**/*</include>
    			</includes>
    		</fileSet>
    		<fileSet>
    			<directory>${basedir}/src/test/resources/contracts</directory>
    			<outputDirectory>META-INF/${project.groupId}/${project.artifactId}/${project.version}/contracts</outputDirectory>
    			<includes>
    				<include>**/*.groovy</include>
    			</includes>
    		</fileSet>
    	</fileSets>
    </assembly>

Gradle

    ext {
    	contractsDir = file("mappings")
    	stubsOutputDirRoot = file("${project.buildDir}/production/${project.name}-stubs/")
    }

    // Automatically added by plugin:
    // copyContracts - copies contracts to the output folder from which JAR will be created
    // verifierStubsJar - JAR with a provided stub suffix
    // the presented publication is also added by the plugin but you can modify it as you wish

    publishing {
    	publications {
    		stubs(MavenPublication) {
    			artifactId "${project.name}-stubs"
    			artifact verifierStubsJar
    		}
    	}
    }

#### Modules

### Stub Runner Core

Runs stubs for service collaborators. Treating stubs as contracts of services allows to use stub-runner as an implementation of Consumer Driven Contracts.

Stub Runner allows you to automatically download the stubs of the provided dependencies, start WireMock servers for them and feed them with proper stub definitions. For messaging, special stub routes are defined.

#### Running stubs

##### Limitations

Important

There might be a problem with StubRunner shutting down ports between tests. You might have a situation in which you get port conflicts. As long as you use the same context across tests everything works fine. But when the context are different (e.g. different stubs or different profiles) then you have to either use `@DirtiesContext` to shut down the stub servers, or else run them on different ports per test.

##### Running using main app

You can set the following options to the main class:

    -c, --classifier                Suffix for the jar containing stubs (e.
                                      g. 'stubs' if the stub jar would
                                      have a 'stubs' classifier for stubs:
                                      foobar-stubs ). Defaults to 'stubs'
                                      (default: stubs)
    --maxPort, --maxp <Integer>     Maximum port value to be assigned to
                                      the WireMock instance. Defaults to
                                      15000 (default: 15000)
    --minPort, --minp <Integer>     Minimum port value to be assigned to
                                      the WireMock instance. Defaults to
                                      10000 (default: 10000)
    -p, --password                  Password to user when connecting to
                                      repository
    --phost, --proxyHost            Proxy host to use for repository
                                      requests
    --pport, --proxyPort [Integer]  Proxy port to use for repository
                                      requests
    -r, --root                      Location of a Jar containing server
                                      where you keep your stubs (e.g. http:
                                      //nexus.
                                      net/content/repositories/repository)
    -s, --stubs                     Comma separated list of Ivy
                                      representation of jars with stubs.
                                      Eg. groupid:artifactid1,groupid2:
                                      artifactid2:classifier
    -u, --username                  Username to user when connecting to
                                      repository
    --wo, --workOffline             Switch to work offline. Defaults to
                                      'false'

##### HTTP Stubs

Stubs are defined in JSON documents, whose syntax is defined in WireMock documentation

Example:

    {
        "request": {
            "method": "GET",
            "url": "/ping"
        },
        "response": {
            "status": 200,
            "body": "pong",
            "headers": {
                "Content-Type": "text/plain"
            }
        }
    }

##### Viewing registered mappings

Every stubbed collaborator exposes list of defined mappings under `__/admin/` endpoint.

##### Messaging Stubs

Depending on the provided Stub Runner dependency and the DSL the messaging routes are automatically set up.

### Stub Runner JUnit Rule

Stub Runner comes with a JUnit rule thanks to which you can very easily download and run stubs for given group and artifact id:

    @ClassRule public static StubRunnerRule rule = new StubRunnerRule()
    		.repoRoot(repoRoot())
    		.downloadStub("org.springframework.cloud.contract.verifier.stubs", "loanIssuance")
    		.downloadStub("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer");

After that rule gets executed Stub Runner connects to your Maven repository and for the given list of dependencies tries to:

- download them

- cache them locally

- unzip them to a temporary folder

- start a WireMock server for each Maven dependency on a random port from the provided range of ports / provided port

- feed the WireMock server with all JSON files that are valid WireMock definitions

Stub Runner uses Eclipse Aether mechanism to download the Maven dependencies. Check their docs for more information.

Since the `StubRunnerRule` implements the `StubFinder` it allows you to find the started stubs:

    /*
     *  Copyright 2013-2017 the original author or authors.
     *
     *  Licensed under the Apache License, Version 2.0 (the "License");
     *  you may not use this file except in compliance with the License.
     *  You may obtain a copy of the License at
     *
     *       http://www.apache.org/licenses/LICENSE-2.0
     *
     *  Unless required by applicable law or agreed to in writing, software
     *  distributed under the License is distributed on an "AS IS" BASIS,
     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     *  See the License for the specific language governing permissions and
     *  limitations under the License.
     */

    package org.springframework.cloud.contract.stubrunner;

    import java.net.URL;
    import java.util.Collection;
    import java.util.Map;

    import org.springframework.cloud.contract.spec.Contract;

    public interface StubFinder extends StubTrigger {
    	/**
    	 * For the given groupId and artifactId tries to find the matching
    	 * URL of the running stub.
    	 *
    	 * @param groupId - might be null. In that case a search only via artifactId takes place
    	 * @return URL of a running stub or throws exception if not found
    	 */
    	URL findStubUrl(String groupId, String artifactId) throws StubNotFoundException;

    	/**
    	 * For the given Ivy notation {@code [groupId]:artifactId:[version]:[classifier]} tries to
    	 * find the matching URL of the running stub. You can also pass only {@code artifactId}.
    	 *
    	 * @param ivyNotation - Ivy representation of the Maven artifact
    	 * @return URL of a running stub or throws exception if not found
    	 */
    	URL findStubUrl(String ivyNotation) throws StubNotFoundException;

    	/**
    	 * Returns all running stubs
    	 */
    	RunningStubs findAllRunningStubs();

    	/**
    	 * Returns the list of Contracts
    	 */
    	Map<StubConfiguration, Collection<Contract>> getContracts();
    }

Example of usage in Spock tests:

    @ClassRule @Shared StubRunnerRule rule = new StubRunnerRule()
    		.repoRoot(StubRunnerRuleSpec.getResource("/m2repo/repository").toURI().toString())
    		.downloadStub("org.springframework.cloud.contract.verifier.stubs", "loanIssuance")
    		.downloadStub("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer")

    def 'should start WireMock servers'() {
    	expect: 'WireMocks are running'
    		rule.findStubUrl('org.springframework.cloud.contract.verifier.stubs', 'loanIssuance') != null
    		rule.findStubUrl('loanIssuance') != null
    		rule.findStubUrl('loanIssuance') == rule.findStubUrl('org.springframework.cloud.contract.verifier.stubs', 'loanIssuance')
    		rule.findStubUrl('org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer') != null
    	and:
    		rule.findAllRunningStubs().isPresent('loanIssuance')
    		rule.findAllRunningStubs().isPresent('org.springframework.cloud.contract.verifier.stubs', 'fraudDetectionServer')
    		rule.findAllRunningStubs().isPresent('org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer')
    	and: 'Stubs were registered'
    		"${rule.findStubUrl('loanIssuance').toString()}/name".toURL().text == 'loanIssuance'
    		"${rule.findStubUrl('fraudDetectionServer').toString()}/name".toURL().text == 'fraudDetectionServer'
    }

Example of usage in JUnit tests:

    @Test
    public void should_start_wiremock_servers() throws Exception {
    	// expect: 'WireMocks are running'
    		then(rule.findStubUrl("org.springframework.cloud.contract.verifier.stubs", "loanIssuance")).isNotNull();
    		then(rule.findStubUrl("loanIssuance")).isNotNull();
    		then(rule.findStubUrl("loanIssuance")).isEqualTo(rule.findStubUrl("org.springframework.cloud.contract.verifier.stubs", "loanIssuance"));
    		then(rule.findStubUrl("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer")).isNotNull();
    	// and:
    		then(rule.findAllRunningStubs().isPresent("loanIssuance")).isTrue();
    		then(rule.findAllRunningStubs().isPresent("org.springframework.cloud.contract.verifier.stubs", "fraudDetectionServer")).isTrue();
    		then(rule.findAllRunningStubs().isPresent("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer")).isTrue();
    	// and: 'Stubs were registered'
    		then(httpGet(rule.findStubUrl("loanIssuance").toString() + "/name")).isEqualTo("loanIssuance");
    		then(httpGet(rule.findStubUrl("fraudDetectionServer").toString() + "/name")).isEqualTo("fraudDetectionServer");
    }

Check the Common properties for JUnit and Spring for more information on how to apply global configuration of Stub Runner.

#### Maven settings

The stub downloader honors Maven settings for a different local repository folder. Authentication details for repositories and profiles are currently not taken into account, so you need to specify it using the properties mentioned above.

#### Providing fixed ports

You can also run your stubs on fixed ports. You can do it in two different ways. One is to pass it in the properties, and the other via fluent API of JUnit rule.

#### Fluent API

When using the `StubRunnerRule` you can add a stub to download and then pass the port for the last downloaded stub.

    @ClassRule public static StubRunnerRule rule = new StubRunnerRule()
    		.repoRoot(repoRoot())
    		.downloadStub("org.springframework.cloud.contract.verifier.stubs", "loanIssuance")
    		.withPort(12345)
    		.downloadStub("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer:12346");

You can see that for this example the following test is valid:

    then(rule.findStubUrl("loanIssuance")).isEqualTo(URI.create("http://localhost:12345").toURL());
    then(rule.findStubUrl("fraudDetectionServer")).isEqualTo(URI.create("http://localhost:12346").toURL());

#### Stub Runner with Spring

Sets up Spring configuration of the Stub Runner project.

By providing a list of stubs inside your configuration file the Stub Runner automatically downloads and registers in WireMock the selected stubs.

If you want to find the URL of your stubbed dependency you can autowire the `StubFinder` interface and use its methods as presented below:

    @ContextConfiguration(classes = Config, loader = SpringBootContextLoader)
    @SpringBootTest(properties = [" stubrunner.cloud.enabled=false",
    		"stubrunner.camel.enabled=false",
    		'foo=${stubrunner.runningstubs.fraudDetectionServer.port}'])
    @AutoConfigureStubRunner
    @DirtiesContext
    @ActiveProfiles("test")
    class StubRunnerConfigurationSpec extends Specification {

    	@Autowired StubFinder stubFinder
    	@Autowired Environment environment
    	@Value('${foo}') Integer foo

    	@BeforeClass
    	@AfterClass
    	void setupProps() {
    		System.clearProperty("stubrunner.repository.root")
    		System.clearProperty("stubrunner.classifier")
    	}

    	def 'should start WireMock servers'() {
    		expect: 'WireMocks are running'
    			stubFinder.findStubUrl('org.springframework.cloud.contract.verifier.stubs', 'loanIssuance') != null
    			stubFinder.findStubUrl('loanIssuance') != null
    			stubFinder.findStubUrl('loanIssuance') == stubFinder.findStubUrl('org.springframework.cloud.contract.verifier.stubs', 'loanIssuance')
    			stubFinder.findStubUrl('loanIssuance') == stubFinder.findStubUrl('org.springframework.cloud.contract.verifier.stubs:loanIssuance')
    			stubFinder.findStubUrl('org.springframework.cloud.contract.verifier.stubs:loanIssuance:0.0.1-SNAPSHOT') == stubFinder.findStubUrl('org.springframework.cloud.contract.verifier.stubs:loanIssuance:0.0.1-SNAPSHOT:stubs')
    			stubFinder.findStubUrl('org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer') != null
    		and:
    			stubFinder.findAllRunningStubs().isPresent('loanIssuance')
    			stubFinder.findAllRunningStubs().isPresent('org.springframework.cloud.contract.verifier.stubs', 'fraudDetectionServer')
    			stubFinder.findAllRunningStubs().isPresent('org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer')
    		and: 'Stubs were registered'
    			"${stubFinder.findStubUrl('loanIssuance').toString()}/name".toURL().text == 'loanIssuance'
    			"${stubFinder.findStubUrl('fraudDetectionServer').toString()}/name".toURL().text == 'fraudDetectionServer'
    	}

    	def 'should throw an exception when stub is not found'() {
    		when:
    			stubFinder.findStubUrl('nonExistingService')
    		then:
    			thrown(StubNotFoundException)
    		when:
    			stubFinder.findStubUrl('nonExistingGroupId', 'nonExistingArtifactId')
    		then:
    			thrown(StubNotFoundException)
    	}

    	def 'should register started servers as environment variables'() {
    		expect:
    			environment.getProperty("stubrunner.runningstubs.loanIssuance.port") != null
    			stubFinder.findAllRunningStubs().getPort("loanIssuance") == (environment.getProperty("stubrunner.runningstubs.loanIssuance.port") as Integer)
    		and:
    			environment.getProperty("stubrunner.runningstubs.fraudDetectionServer.port") != null
    			stubFinder.findAllRunningStubs().getPort("fraudDetectionServer") == (environment.getProperty("stubrunner.runningstubs.fraudDetectionServer.port") as Integer)
    	}

    	def 'should be able to interpolate a running stub in the passed test property'() {
    		given:
    			int fraudPort = stubFinder.findAllRunningStubs().getPort("fraudDetectionServer")
    		expect:
    			fraudPort > 0
    			environment.getProperty("foo", Integer) == fraudPort
    			foo == fraudPort
    	}

    	@Configuration
    	@EnableAutoConfiguration
    	static class Config {}
    }

for the following configuration file:

    stubrunner:
      repositoryRoot: classpath:m2repo/repository/
      ids:
        - org.springframework.cloud.contract.verifier.stubs:loanIssuance
        - org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer
        - org.springframework.cloud.contract.verifier.stubs:bootService

Instead of using the properties you can also use the properties inside the `@AutoConfigureStubRunner`. Below you can find an example of achieving the same result by setting values on the annotation.

    @AutoConfigureStubRunner(
    		ids = ["org.springframework.cloud.contract.verifier.stubs:loanIssuance",
    		"org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer",
    		"org.springframework.cloud.contract.verifier.stubs:bootService"],
    		repositoryRoot = "classpath:m2repo/repository/")

Stub Runner Spring registers environment variables in the following manner for every registered WireMock server. Example for Stub Runner ids `com.example:foo`, `com.example:bar`.

- `stubrunner.runningstubs.foo.port`

- `stubrunner.runningstubs.bar.port`

Which you can reference in your code.

### Stub Runner Spring Cloud

Stub Runner can integrate with Spring Cloud.

For real life examples you can check the

- producer app sample

- consumer app sample

#### Stubbing Service Discovery

The most important feature of `Stub Runner Spring Cloud` is the fact that it’s stubbing

- `DiscoveryClient`

- `Ribbon` `ServerList`

that means that regardless of the fact whether you’re using Zookeeper, Consul, Eureka or anything else, you don’t need that in your tests. We’re starting WireMock instances of your dependencies and we’re telling your application whenever you’re using `Feign`, load balanced `RestTemplate` or `DiscoveryClient` directly, to call those stubbed servers instead of calling the real Service Discovery tool.

For example this test will pass

    def 'should make service discovery work'() {
    	expect: 'WireMocks are running'
    		"${stubFinder.findStubUrl('loanIssuance').toString()}/name".toURL().text == 'loanIssuance'
    		"${stubFinder.findStubUrl('fraudDetectionServer').toString()}/name".toURL().text == 'fraudDetectionServer'
    	and: 'Stubs can be reached via load service discovery'
    		restTemplate.getForObject('http://loanIssuance/name', String) == 'loanIssuance'
    		restTemplate.getForObject('http://someNameThatShouldMapFraudDetectionServer/name', String) == 'fraudDetectionServer'
    }

for the following configuration file

    spring.cloud:
      zookeeper.enabled: false
      consul.enabled: false
    eureka.client.enabled: false
    stubrunner:
      camel.enabled: false
      idsToServiceIds:
        ivyNotation: someValueInsideYourCode
        fraudDetectionServer: someNameThatShouldMapFraudDetectionServer

##### Test profiles and service discovery

In your integration tests you typically don’t want to call neither a discovery service (e.g. Eureka) or Config Server. That’s why you create an additional test configuration in which you want to disable these features.

Due to certain limitations of `spring-cloud-commons` to achieve this you have disable these properties via a static block like presented below (example for Eureka)

        //Hack to work around https://github.com/spring-cloud/spring-cloud-commons/issues/156
        static {
            System.setProperty("eureka.client.enabled", "false");
            System.setProperty("spring.cloud.config.failFast", "false");
        }

#### Additional Configuration

You can match the artifactId of the stub with the name of your app by using the `stubrunner.idsToServiceIds:` map. You can disable Stub Runner Ribbon support by providing: `stubrunner.cloud.ribbon.enabled` equal to `false` You can disable Stub Runner support by providing: `stubrunner.cloud.enabled` equal to `false`

Tip | By default all service discovery will be stubbed. That means that regardless of the fact if you have an existing `DiscoveryClient` its results will be ignored. However, if you want to reuse it, just set `stubrunner.cloud.delegate.enabled` to `true` and then your existing `DiscoveryClient` results will be merged with the stubbed ones.

### Stub Runner Boot Application

Spring Cloud Contract Verifier Stub Runner Boot is a Spring Boot application that exposes REST endpoints to trigger the messaging labels and to access started WireMock servers.

One of the use-cases is to run some smoke (end to end) tests on a deployed application. You can read more about this in the "Microservice Deployment" article at Too Much Coding blog.

#### How to use it?

Just add the

    compile "org.springframework.cloud:spring-cloud-starter-stub-runner"

Annotate a class with `@EnableStubRunnerServer`, build a fat-jar and you’re ready to go!

For the properties check the Stub Runner Spring section.

#### Endpoints

##### HTTP

- GET `/stubs` - returns a list of all running stubs in `ivy:integer` notation

- GET `/stubs/{ivy}` - returns a port for the given `ivy` notation (when calling the endpoint `ivy` can also be `artifactId` only)

##### Messaging

For Messaging

- GET `/triggers` - returns a list of all running labels in `ivy : [ label1, label2 …​]` notation

- POST `/triggers/{label}` - executes a trigger with `label`

- POST `/triggers/{ivy}/{label}` - executes a trigger with `label` for the given `ivy` notation (when calling the endpoint `ivy` can also be `artifactId` only)

#### Example

    @ContextConfiguration(classes = StubRunnerBoot, loader = SpringBootContextLoader)
    @SpringBootTest(properties = "spring.cloud.zookeeper.enabled=false")
    @ActiveProfiles("test")
    class StubRunnerBootSpec extends Specification {

    	@Autowired StubRunning stubRunning

    	def setup() {
    		RestAssuredMockMvc.standaloneSetup(new HttpStubsController(stubRunning),
    				new TriggerController(stubRunning))
    	}

    	def 'should return a list of running stub servers in "full ivy:port" notation'() {
    		when:
    			String response = RestAssuredMockMvc.get('/stubs').body.asString()
    		then:
    			def root = new JsonSlurper().parseText(response)
    			root.'org.springframework.cloud.contract.verifier.stubs:bootService:0.0.1-SNAPSHOT:stubs' instanceof Integer
    	}

    	def 'should return a port on which a [#stubId] stub is running'() {
    		when:
    			def response = RestAssuredMockMvc.get("/stubs/${stubId}")
    		then:
    			response.statusCode == 200
    			response.body.as(Integer) > 0
    		where:
    			stubId << ['org.springframework.cloud.contract.verifier.stubs:bootService:+:stubs',
    					   'org.springframework.cloud.contract.verifier.stubs:bootService:0.0.1-SNAPSHOT:stubs',
    					   'org.springframework.cloud.contract.verifier.stubs:bootService:+',
    					   'org.springframework.cloud.contract.verifier.stubs:bootService',
    					   'bootService']
    	}

    	def 'should return 404 when missing stub was called'() {
    		when:
    			def response = RestAssuredMockMvc.get("/stubs/a:b:c:d")
    		then:
    			response.statusCode == 404
    	}

    	def 'should return a list of messaging labels that can be triggered when version and classifier are passed'() {
    		when:
    			String response = RestAssuredMockMvc.get('/triggers').body.asString()
    		then:
    			def root = new JsonSlurper().parseText(response)
    			root.'org.springframework.cloud.contract.verifier.stubs:bootService:0.0.1-SNAPSHOT:stubs'?.containsAll(["delete_book","return_book_1","return_book_2"])
    	}

    	def 'should trigger a messaging label'() {
    		given:
    			StubRunning stubRunning = Mock()
    			RestAssuredMockMvc.standaloneSetup(new HttpStubsController(stubRunning), new TriggerController(stubRunning))
    		when:
    			def response = RestAssuredMockMvc.post("/triggers/delete_book")
    		then:
    			response.statusCode == 200
    		and:
    			1 * stubRunning.trigger('delete_book')
    	}

    	def 'should trigger a messaging label for a stub with [#stubId] ivy notation'() {
    		given:
    			StubRunning stubRunning = Mock()
    			RestAssuredMockMvc.standaloneSetup(new HttpStubsController(stubRunning), new TriggerController(stubRunning))
    		when:
    			def response = RestAssuredMockMvc.post("/triggers/$stubId/delete_book")
    		then:
    			response.statusCode == 200
    		and:
    			1 * stubRunning.trigger(stubId, 'delete_book')
    		where:
    			stubId << ['org.springframework.cloud.contract.verifier.stubs:bootService:stubs', 'org.springframework.cloud.contract.verifier.stubs:bootService', 'bootService']
    	}

    	def 'should throw exception when trigger is missing'() {
    		when:
    			RestAssuredMockMvc.post("/triggers/missing_label")
    		then:
    			Exception e = thrown(Exception)
    			e.message.contains("Exception occurred while trying to return [missing_label] label.")
    			e.message.contains("Available labels are")
    			e.message.contains("org.springframework.cloud.contract.verifier.stubs:loanIssuance:0.0.1-SNAPSHOT:stubs=[]")
    			e.message.contains("org.springframework.cloud.contract.verifier.stubs:bootService:0.0.1-SNAPSHOT:stubs=")
    	}

    }

#### Stub Runner Boot with Service Discovery

One of the possibilities of using Stub Runner Boot is to use it as a feed of stubs for "smoke-tests". What does it mean? Let’s assume that you don’t want to deploy 50 microservice to a test environment in order to check if your application is working fine. You’ve already executed a suite of tests during the build process but you would also like to ensure that the packaging of your application is fine. What you can do is to deploy your application to an environment, start it and run a couple of tests on it to see if it’s working fine. We can call those tests smoke-tests since their idea is to check only a handful of testing scenarios.

The problem with this approach is such that if you’re doing microservices most likely you’re using a service discovery tool. Stub Runner Boot allows you to solve this issue by starting the required stubs and register them in a service discovery tool. Let’s take a look at an example of such a setup with Eureka. Let’s assume that Eureka was already running.

    @SpringBootApplication
    @EnableStubRunnerServer
    @EnableEurekaClient
    @AutoConfigureStubRunner
    public class StubRunnerBootEurekaExample {

    	public static void main(String[] args) {
    		SpringApplication.run(StubRunnerBootEurekaExample.class, args);
    	}

    }

As you can see we want to start a Stub Runner Boot server `@EnableStubRunnerServer`, enable Eureka client `@EnableEurekaClient` and we want to have the stub runner feature turned on `@AutoConfigureStubRunner`.

Now let’s assume that we want to start this application so that the stubs get automatically registered. We can do it by running the app `java -jar ${SYSTEM_PROPS} stub-runner-boot-eureka-example.jar` where `${SYSTEM_PROPS}` would contain the following list of properties

    -Dstubrunner.repositoryRoot=http://repo.spring.io/snapshots (1)
    -Dstubrunner.cloud.stubbed.discovery.enabled=false (2)
    -Dstubrunner.ids=org.springframework.cloud.contract.verifier.stubs:loanIssuance,org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer,org.springframework.cloud.contract.verifier.stubs:bootService (3)
    -Dstubrunner.idsToServiceIds.fraudDetectionServer=someNameThatShouldMapFraudDetectionServer (4)

    (1) - we tell Stub Runner where all the stubs reside
    (2) - we don't want the default behaviour where the discovery service is stubbed. That's why the stub registration will be picked
    (3) - we provide a list of stubs to download
    (4) - we provide a list of artifactId to serviceId mapping

That way your deployed application can send requests to started WireMock servers via the service discovery. Most likely points 1-3 could be set by default in `application.yml` cause they are not likely to change. That way you can provide only the list of stubs to download whenever you start the Stub Runner Boot.

#### Common properties for JUnit and Spring

Some of the properties that are repetitive can be set using system properties or configuration properties (for Spring). Here are their names with their default values:

Property name | Default value | Description
--- | --- | ---
stubrunner.minPort | 10000 | Minimal value of a port for a started WireMock with stubs
stubrunner.maxPort | 15000 | Minimal value of a port for a started WireMock with stubs
stubrunner.repositoryRoot |  | Maven repo url. If blank then will call the local maven repo
stubrunner.classifier | stubs | Default classifier for the stub artifacts
stubrunner.workOffline | false | If true then will not contact any remote repositories to download stubs
stubrunner.ids |  | Array of Ivy notation stubs to download
stubrunner.username |  | Optional username to access the tool that stores the JARs with stubs
stubrunner.password |  | Optional password to access the tool that stores the JARs with stubs

##### Stub runner stubs ids

You can provide the stubs to download via the `stubrunner.ids` system property. They follow the following pattern:

    groupId:artifactId:version:classifier:port

`version`, `classifier` and `port` are optional.

- If you don’t provide the `port` then a random one will be picked

- If you don’t provide the `classifier` then the default one will be taken. (NOTE that you can pass an empty classifier like this `groupId:artifactId:version:`)

- If you don’t provide the `version` then the `+` will be passed and the latest one will be downloaded

Where `port` means the port of the WireMock server.

Important | Starting from version 1.0.4 as a version you can provide a range of versions that you would like the Stub Runner to take into consideration. You can read more about the Aether versioning ranges here.

Taken from Aether Docs:

> This scheme accepts versions of any form, interpreting a version as a sequence of numeric and alphabetic segments. The characters '-', '_', and '.' as well as the mere transitions from digit to letter and vice versa delimit the version segments. Delimiters are treated as equivalent.

> Numeric segments are compared mathematically, alphabetic segments are compared lexicographically and case-insensitively. However, the following qualifier strings are recognized and treated specially: "alpha" = "a" < "beta" = "b" < "milestone" = "m" < "cr" = "rc" < "snapshot" < "final" = "ga" < "sp". All of those well-known qualifiers are considered smaller/older than other strings. An empty segment/string is equivalent to 0.

> In addition to the above mentioned qualifiers, the tokens "min" and "max" may be used as final version segment to denote the smallest/greatest version having a given prefix. For example, "1.2.min" denotes the smallest version in the 1.2 line, "1.2.max" denotes the greatest version in the 1.2 line. A version range of the form "[M.N.*]" is short for "[M.N.min, M.N.max]".

> Numbers and strings are considered incomparable against each other. Where version segments of different kind would collide, comparison will instead assume that the previous segments are padded with trailing 0 or "ga" segments, respectively, until the kind mismatch is resolved, e.g. "1-alpha" = "1.0.0-alpha" < "1.0.1-ga" = "1.0.1".

### Stub Runner for Messaging

Stub Runner has the functionality to run the published stubs in memory. It can integrate with the following frameworks out of the box

- Spring Integration

- Spring Cloud Stream

- Apache Camel

- Spring AMQP

It also provides points of entry to integrate with any other solution on the market.

#### Stub triggering

To trigger a message it’s enough to use the `StubTrigger` interface:

    /*
     *  Copyright 2013-2017 the original author or authors.
     *
     *  Licensed under the Apache License, Version 2.0 (the "License");
     *  you may not use this file except in compliance with the License.
     *  You may obtain a copy of the License at
     *
     *       http://www.apache.org/licenses/LICENSE-2.0
     *
     *  Unless required by applicable law or agreed to in writing, software
     *  distributed under the License is distributed on an "AS IS" BASIS,
     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     *  See the License for the specific language governing permissions and
     *  limitations under the License.
     */

    package org.springframework.cloud.contract.stubrunner;

    import java.util.Collection;
    import java.util.Map;

    public interface StubTrigger {

    	/**
    	 * Triggers an event by a given label for a given {@code groupid:artifactid} notation. You can use only {@code artifactId} too.
    	 *
    	 * Feature related to messaging.
    	 *
    	 * @return true - if managed to run a trigger
    	 */
    	boolean trigger(String ivyNotation, String labelName);

    	/**
    	 * Triggers an event by a given label.
    	 *
    	 * Feature related to messaging.
    	 *
    	 * @return true - if managed to run a trigger
    	 */
    	boolean trigger(String labelName);

    	/**
    	 * Triggers all possible events.
    	 *
    	 * Feature related to messaging.
    	 *
    	 * @return true - if managed to run a trigger
    	 */
    	boolean trigger();

    	/**
    	 * Returns a mapping of ivy notation of a dependency to all the labels it has.
    	 *
    	 * Feature related to messaging.
    	 */
    	Map<String, Collection<String>> labels();
    }

For convenience the `StubFinder` interface extends `StubTrigger` so it’s enough to use only one in your tests.

`StubTrigger` gives you the following options to trigger a message:

##### Trigger by label

    stubFinder.trigger('return_book_1')

###### Trigger by group and artifact ids

    stubFinder.trigger('org.springframework.cloud.contract.verifier.stubs:camelService', 'return_book_1')

###### Trigger by artifact ids

    stubFinder.trigger('camelService', 'return_book_1')

##### Trigger all messages

    stubFinder.trigger()

### Stub Runner Camel

Spring Cloud Contract Verifier Stub Runner’s messaging module gives you an easy way to integrate with Apache Camel. For the provided artifacts it will automatically download the stubs and register the required routes.

#### Adding it to the project

It’s enough to have both Apache Camel and Spring Cloud Contract Stub Runner on classpath. Remember to annotate your test class with `@AutoConfigureMessageVerifier`.

#### Examples

##### Stubs structure

Let us assume that we have the following Maven repository with a deployed stubs for the `camelService` application.

    └── .m2
        └── repository
            └── io
                └── codearte
                    └── accurest
                        └── stubs
                            └── camelService
                                ├── 0.0.1-SNAPSHOT
                                │   ├── camelService-0.0.1-SNAPSHOT.pom
                                │   ├── camelService-0.0.1-SNAPSHOT-stubs.jar
                                │   └── maven-metadata-local.xml
                                └── maven-metadata-local.xml

And the stubs contain the following structure:

    ├── META-INF
    │   └── MANIFEST.MF
    └── repository
        ├── accurest
        │   ├── bookDeleted.groovy
        │   ├── bookReturned1.groovy
        │   └── bookReturned2.groovy
        └── mappings

Let’s consider the following contracts (let' number it with 1):

    Contract.make {
    	label 'return_book_1'
    	input {
    		triggeredBy('bookReturnedTriggered()')
    	}
    	outputMessage {
    		sentTo('jms:output')
    		body('''{ "bookName" : "foo" }''')
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

and number 2

    Contract.make {
    	label 'return_book_2'
    	input {
    		messageFrom('jms:input')
    		messageBody([
    				bookName: 'foo'
    		])
    		messageHeaders {
    			header('sample', 'header')
    		}
    	}
    	outputMessage {
    		sentTo('jms:output')
    		body([
    				bookName: 'foo'
    		])
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

##### Scenario 1 (no input message)

So as to trigger a message via the `return_book_1` label we’ll use the `StubTigger` interface as follows

    stubFinder.trigger('return_book_1')

Next we’ll want to listen to the output of the message sent to `jms:output`

    Exchange receivedMessage = camelContext.createConsumerTemplate().receive('jms:output', 5000)

And the received message would pass the following assertions

    receivedMessage != null
    assertThatBodyContainsBookNameFoo(receivedMessage.in.body)
    receivedMessage.in.headers.get('BOOK-NAME') == 'foo'

##### Scenario 2 (output triggered by input)

Since the route is set for you it’s enough to just send a message to the `jms:output` destination.

    camelContext.createProducerTemplate().sendBodyAndHeaders('jms:input', new BookReturned('foo'), [sample: 'header'])

Next we’ll want to listen to the output of the message sent to `jms:output`

    Exchange receivedMessage = camelContext.createConsumerTemplate().receive('jms:output', 5000)

And the received message would pass the following assertions

    receivedMessage != null
    assertThatBodyContainsBookNameFoo(receivedMessage.in.body)
    receivedMessage.in.headers.get('BOOK-NAME') == 'foo'

##### Scenario 3 (input with no output)

Since the route is set for you it’s enough to just send a message to the `jms:output` destination.

    camelContext.createProducerTemplate().sendBodyAndHeaders('jms:delete', new BookReturned('foo'), [sample: 'header'])

### Stub Runner Integration

Spring Cloud Contract Verifier Stub Runner’s messaging module gives you an easy way to integrate with Spring Integration. For the provided artifacts it will automatically download the stubs and register the required routes.

#### Adding it to the project

It’s enough to have both Apache Camel and Spring Cloud Contract Stub Runner on classpath. Remember to annotate your test class with `@AutoConfigureMessageVerifier`.

#### Examples

##### Stubs structure

Let us assume that we have the following Maven repository with a deployed stubs for the `integrationService` application.

    └── .m2
        └── repository
            └── io
                └── codearte
                    └── accurest
                        └── stubs
                            └── integrationService
                                ├── 0.0.1-SNAPSHOT
                                │   ├── integrationService-0.0.1-SNAPSHOT.pom
                                │   ├── integrationService-0.0.1-SNAPSHOT-stubs.jar
                                │   └── maven-metadata-local.xml
                                └── maven-metadata-local.xml

And the stubs contain the following structure:

    ├── META-INF
    │   └── MANIFEST.MF
    └── repository
        ├── accurest
        │   ├── bookDeleted.groovy
        │   ├── bookReturned1.groovy
        │   └── bookReturned2.groovy
        └── mappings

Let’s consider the following contracts (let' number it with 1):

    Contract.make {
    	label 'return_book_1'
    	input {
    		triggeredBy('bookReturnedTriggered()')
    	}
    	outputMessage {
    		sentTo('output')
    		body('''{ "bookName" : "foo" }''')
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

and number 2

    Contract.make {
    	label 'return_book_2'
    	input {
    		messageFrom('input')
    		messageBody([
    				bookName: 'foo'
    		])
    		messageHeaders {
    			header('sample', 'header')
    		}
    	}
    	outputMessage {
    		sentTo('output')
    		body([
    				bookName: 'foo'
    		])
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

and the following Spring Integration Route:

    <?xml version="1.0" encoding="UTF-8"?>
    <!--
      ~  Copyright 2013-2017 the original author or authors.
      ~
      ~  Licensed under the Apache License, Version 2.0 (the "License");
      ~  you may not use this file except in compliance with the License.
      ~  You may obtain a copy of the License at
      ~
      ~       http://www.apache.org/licenses/LICENSE-2.0
      ~
      ~  Unless required by applicable law or agreed to in writing, software
      ~  distributed under the License is distributed on an "AS IS" BASIS,
      ~  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      ~  See the License for the specific language governing permissions and
      ~  limitations under the License.
      -->

    <beans:beans xmlns="http://www.springframework.org/schema/integration"
    			 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    			 xmlns:beans="http://www.springframework.org/schema/beans"
    			 xsi:schemaLocation="http://www.springframework.org/schema/beans
    			http://www.springframework.org/schema/beans/spring-beans.xsd
    			http://www.springframework.org/schema/integration
    			http://www.springframework.org/schema/integration/spring-integration.xsd">

    	<!-- REQUIRED FOR TESTING -->
    	<bridge input-channel="output"
    			output-channel="outputTest"/>

    	<channel id="outputTest">
    		<queue/>
    	</channel>

    </beans:beans>

##### Scenario 1 (no input message)

So as to trigger a message via the `return_book_1` label we’ll use the `StubTigger` interface as follows

    stubFinder.trigger('return_book_1')

Next we’ll want to listen to the output of the message sent to `output`

    Message<?> receivedMessage = messaging.receive('outputTest')

And the received message would pass the following assertions

    receivedMessage != null
    assertJsons(receivedMessage.payload)
    receivedMessage.headers.get('BOOK-NAME') == 'foo'

##### Scenario 2 (output triggered by input)

Since the route is set for you it’s enough to just send a message to the `output` destination.

    messaging.send(new BookReturned('foo'), [sample: 'header'], 'input')

Next we’ll want to listen to the output of the message sent to `output`

    Message<?> receivedMessage = messaging.receive('outputTest')

And the received message would pass the following assertions

    receivedMessage != null
    assertJsons(receivedMessage.payload)
    receivedMessage.headers.get('BOOK-NAME') == 'foo'

##### Scenario 3 (input with no output)

Since the route is set for you it’s enough to just send a message to the `input` destination.

    messaging.send(new BookReturned('foo'), [sample: 'header'], 'delete')

### Stub Runner Stream

Spring Cloud Contract Verifier Stub Runner’s messaging module gives you an easy way to integrate with Spring Stream. For the provided artifacts it will automatically download the stubs and register the required routes.

Warning | In Stub Runner’s integration with Stream the `messageFrom` or `sentTo` Strings are resolved first as a `destination` of a channel, and then if there is no such `destination` it’s resolved as a channel name.

#### Adding it to the project

It’s enough to have both Apache Camel and Spring Cloud Contract Stub Runner on classpath. Remember to annotate your test class with `@AutoConfigureMessageVerifier`.

#### Examples

##### Stubs structure

Let us assume that we have the following Maven repository with a deployed stubs for the `streamService` application.

    └── .m2
        └── repository
            └── io
                └── codearte
                    └── accurest
                        └── stubs
                            └── streamService
                                ├── 0.0.1-SNAPSHOT
                                │   ├── streamService-0.0.1-SNAPSHOT.pom
                                │   ├── streamService-0.0.1-SNAPSHOT-stubs.jar
                                │   └── maven-metadata-local.xml
                                └── maven-metadata-local.xml

And the stubs contain the following structure:

    ├── META-INF
    │   └── MANIFEST.MF
    └── repository
        ├── accurest
        │   ├── bookDeleted.groovy
        │   ├── bookReturned1.groovy
        │   └── bookReturned2.groovy
        └── mappings

Let’s consider the following contracts (let' number it with 1):

    Contract.make {
    	label 'return_book_1'
    	input { triggeredBy('bookReturnedTriggered()') }
    	outputMessage {
    		sentTo('returnBook')
    		body('''{ "bookName" : "foo" }''')
    		headers { header('BOOK-NAME', 'foo') }
    	}
    }

and number 2

    Contract.make {
    	label 'return_book_2'
    	input {
    		messageFrom('bookStorage')
    		messageBody([
    			bookName: 'foo'
    		])
    		messageHeaders { header('sample', 'header') }
    	}
    	outputMessage {
    		sentTo('returnBook')
    		body([
    			bookName: 'foo'
    		])
    		headers { header('BOOK-NAME', 'foo') }
    	}
    }

and the following Spring configuration:

    stubrunner.repositoryRoot: classpath:m2repo/repository/
    stubrunner.ids: org.springframework.cloud.contract.verifier.stubs:streamService:0.0.1-SNAPSHOT:stubs

    spring:
      cloud:
        stream:
          bindings:
            output:
              destination: returnBook
            input:
              destination: bookStorage

    server:
      port: 0

##### Scenario 1 (no input message)

So as to trigger a message via the `return_book_1` label we’ll use the `StubTrigger` interface as follows

    stubFinder.trigger('return_book_1')

Next we’ll want to listen to the output of the message sent to a channel whose `destination` is `returnBook`

    Message<?> receivedMessage = messaging.receive('returnBook')

And the received message would pass the following assertions

    receivedMessage != null
    assertJsons(receivedMessage.payload)
    receivedMessage.headers.get('BOOK-NAME') == 'foo'

##### Scenario 2 (output triggered by input)

Since the route is set for you it’s enough to just send a message to the `bookStorage` `destination`.

    messaging.send(new BookReturned('foo'), [sample: 'header'], 'bookStorage')

Next we’ll want to listen to the output of the message sent to `returnBook`

    Message<?> receivedMessage = messaging.receive('returnBook')

And the received message would pass the following assertions

    receivedMessage != null
    assertJsons(receivedMessage.payload)
    receivedMessage.headers.get('BOOK-NAME') == 'foo'

##### Scenario 3 (input with no output)

Since the route is set for you it’s enough to just send a message to the `output` destination.

    messaging.send(new BookReturned('foo'), [sample: 'header'], 'delete')

### Stub Runner Spring AMQP

Spring Cloud Contract Verifier Stub Runner’s messaging module provides an easy way to integrate with Spring AMQP’s Rabbit Template. For the provided artifacts it will automatically download the stubs and register the required routes.

The integration tries to work standalone, that is without interaction with a running RabbitMQ message broker. It expects a `RabbitTemplate` on the application context and uses it as a spring boot test `@SpyBean`. Thus it can use the mockito spy functionality to verify and introspect messages sent by the application.

On the message consumer side, it considers all `@RabbitListener` annotated endpoints as well as all `SimpleMessageListenerContainer`s on the application context.

As messages are usually sent to exchanges in AMQP the message contract contains the exchange name as the destination. Message listeners on the other side are bound to queues. Bindings connect an exchange to a queue. If message contracts are triggered the Spring AMQP stub runner integration will look for bindings on the application context that match this exchange. Then it collects the queues from the Spring exchanges and tries to find messages listeners bound to these queues. The message is triggered to all matching message listeners.

#### Adding it to the project

It’s enough to have both Spring AMQP and Spring Cloud Contract Stub Runner on the classpath and set the property `stubrunner.amqp.enabled=true`. Remember to annotate your test class with `@AutoConfigureMessageVerifier`.

#### Examples

##### Stubs structure

Let us assume that we have the following Maven repository with a deployed stubs for the `spring-cloud-contract-amqp-test` application.

    └── .m2
        └── repository
            └── com
                └── example
                    └── spring-cloud-contract-amqp-test
                        ├── 0.4.0-SNAPSHOT
                        │   ├── spring-cloud-contract-amqp-test-0.4.0-SNAPSHOT.pom
                        │   ├── spring-cloud-contract-amqp-test-0.4.0-SNAPSHOT-stubs.jar
                        │   └── maven-metadata-local.xml
                        └── maven-metadata-local.xml

And the stubs contain the following structure:

    ├── META-INF
    │   └── MANIFEST.MF
    └── contracts
        └── shouldProduceValidPersonData.groovy

Let’s consider the following contract:

    Contract.make {
        // Human readable description
        description 'Should produce valid person data'
        // Label by means of which the output message can be triggered
        label 'contract-test.person.created.event'
        // input to the contract
        input {
            // the contract will be triggered by a method
            triggeredBy('createPerson()')
        }
        // output message of the contract
        outputMessage {
            // destination to which the output message will be sent
            sentTo 'contract-test.exchange'
            headers {
                header('contentType': 'application/json')
                header('__TypeId__': 'org.springframework.cloud.contract.stubrunner.messaging.amqp.Person')
            }
            // the body of the output message
            body ([
                    id: $(consumer(9), producer(regex("[0-9]+"))),
                    name: "me"
            ])
        }
    }

and the following Spring configuration:

    stubrunner:
      repositoryRoot: classpath:m2repo/repository/
      ids: org.springframework.cloud.contract.verifier.stubs.amqp:spring-cloud-contract-amqp-test:0.4.0-SNAPSHOT:stubs
      amqp:
        enabled: true
    server:
      port: 0

##### Triggering the message

So to trigger a message using the contract above we’ll use the `StubTrigger` interface as follows.

    stubTrigger.trigger("contract-test.person.created.event")

The message has the destination `contract-test.exchange` so the Spring AMQP stub runner integration looks for bindings related to this exchange.

    @Bean
    public Binding binding() {
    	return BindingBuilder.bind(new Queue("test.queue")).to(new DirectExchange("contract-test.exchange")).with("#");
    }

The binding definition binds the queue `test.queue`. So the following listener definition is a match and is invoked with the contract message.

    @Bean
    public SimpleMessageListenerContainer simpleMessageListenerContainer(ConnectionFactory connectionFactory,
    																		MessageListenerAdapter listenerAdapter) {
    	SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
    	container.setConnectionFactory(connectionFactory);
    	container.setQueueNames("test.queue");
    	container.setMessageListener(listenerAdapter);

    	return container;
    }

Also, the following annotated listener represents a match and would be invoked.

    @RabbitListener(bindings = @QueueBinding(
    		value = @Queue(value = "test.queue"),
    		exchange = @Exchange(value = "contract-test.exchange", ignoreDeclarationExceptions = "true")))
    public void handlePerson(Person person) {
    	this.person = person;
    }

Note | The message is directly handed over to the `onMessage` method of the `MessageListener` associated with the matching `SimpleMessageListenerContainer`.

##### Spring AMQP Test Configuration

In order to avoid that Spring AMQP is trying to connect to a running broker during our tests we configure a mock `ConnectionFactory`.

To disable the mocked ConnectionFactory set the property `stubrunner.amqp.mockConnection=false`

    stubrunner:
      amqp:
        mockConnection: false

### Contract DSL

Important | Remember that inside the contract file you have to provide the fully qualified name to the `Contract` class and the `make` static import i.e. `org.springframework.cloud.spec.Contract.make { …​ }`. You can also provide an import to the `Contract` class `import org.springframework.cloud.spec.Contract` and then call `Contract.make { …​ }`

Contract DSL is written in Groovy, but don’t be alarmed if you didn’t use Groovy before. Knowledge of the language is not really needed as our DSL uses only a tiny subset of it (namely literals, method calls and closures). What’s more the DSL is designed to be programmer-readable without any knowledge of the DSL itself - it’s statically typed.

The Contract is present in the `spring-cloud-contract-spec` module of the Spring Cloud Contract Verifier repository.

Let’s look at full example of a contract definition.

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		method 'PUT'
    		url '/api/12'
    		headers {
    			header 'Content-Type': 'application/vnd.org.springframework.cloud.contract.verifier.twitter-places-analyzer.v1+json'
    		}
    		body '''\
    		[{
    			"created_at": "Sat Jul 26 09:38:57 +0000 2014",
    			"id": 492967299297845248,
    			"id_str": "492967299297845248",
    			"text": "Gonna see you at Warsaw",
    			"place":
    			{
    				"attributes":{},
    				"bounding_box":
    				{
    					"coordinates":
    						[[
    							[-77.119759,38.791645],
    							[-76.909393,38.791645],
    							[-76.909393,38.995548],
    							[-77.119759,38.995548]
    						]],
    					"type":"Polygon"
    				},
    				"country":"United States",
    				"country_code":"US",
    				"full_name":"Washington, DC",
    				"id":"01fbe706f872cb32",
    				"name":"Washington",
    				"place_type":"city",
    				"url": "http://api.twitter.com/1/geo/id/01fbe706f872cb32.json"
    			}
    		}]
    	'''
    	}
    	response {
    		status 200
    	}
    }

Not all features of the DSL are used in example above. If you didn’t find what you are looking for, please check next paragraphs on this page.

> You can easily compile Contracts to WireMock stubs mapping using standalone maven command: `mvn org.springframework.cloud:spring-cloud-contract-maven-plugin:convert`.

#### Limitations

Warning | Spring Cloud Contract Verifier doesn’t support XML properly. Please use JSON or help us implement this feature.

Warning | Spring Cloud Contract Verifier supports equality check on text response. Regular expressions are not yet available.

Warning | The support for the verification of size of JSON arrays is experimental. If you want to turn it on please provide the value of a system property `spring.cloud.contract.verifier.assert.size` equal to `true`. By default this feature is set to `false`. You can also provide the `assertJsonSize` property in the plugin configuration.

Warning | Due to the fact that JSON structure can have any form it’s sometimes impossible to parse it properly when using the `value(consumer(…​), producer(…​))` notation when using that in GString. That’s why we highly recommend using the Groovy Map notation.

#### Common Top-Level elements

##### Description

You can add a `description` to your contract that is nothing else but an arbitrary text. Example:

    		org.springframework.cloud.contract.spec.Contract.make {
    			description('''
    given:
    	An input
    when:
    	Sth happens
    then:
    	Output
    ''')
    		}

##### Ignoring contracts

If you want to ignore a contract you can either set a value of ignored contracts in the plugin configuration or just set the `ignored` property on the contract itself:

    org.springframework.cloud.contract.spec.Contract.make {
    	ignored()
    }

#### HTTP Top-Level Elements

Following methods can be called in the top-level closure of a contract definition. Request and response are mandatory, priority is optional.

    org.springframework.cloud.contract.spec.Contract.make {
    	// Definition of HTTP request part of the contract
    	// (this can be a valid request or invalid depending
    	// on type of contract being specified).
    	request {
    		//...
    	}

    	// Definition of HTTP response part of the contract
    	// (a service implementing this contract should respond
    	// with following response after receiving request
    	// specified in "request" part above).
    	response {
    		//...
    	}

    	// Contract priority, which can be used for overriding
    	// contracts (1 is highest). Priority is optional.
    	priority 1
    }

#### Request

HTTP protocol requires only method and address to be specified in a request. The same information is mandatory in request definition of the Contract.

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		// HTTP request method (GET/POST/PUT/DELETE).
    		method 'GET'

    		// Path component of request URL is specified as follows.
    		urlPath('/users')
    	}

    	response {
    		//...
    	}
    }

It is possible to specify whole `url` instead of just path, but `urlPath` is the recommended way as it makes the tests host-independent.

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		method 'GET'

    		// Specifying `url` and `urlPath` in one contract is illegal.
    		url('http://localhost:8888/users')
    	}

    	response {
    		//...
    	}
    }

Request may contain query parameters, which are specified in a closure nested in a call to `urlPath` or `url`.

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		//...

    		urlPath('/users') {

    			// Each parameter is specified in form
    			// `'paramName' : paramValue` where parameter value
    			// may be a simple literal or one of matcher functions,
    			// all of which are used in this example.
    			queryParameters {

    				// If a simple literal is used as value
    				// default matcher function is used (equalTo)
    				parameter 'limit': 100

    				// `equalTo` function simply compares passed value
    				// using identity operator (==).
    				parameter 'filter': equalTo("email")

    				// `containing` function matches strings
    				// that contains passed substring.
    				parameter 'gender': value(consumer(containing("[mf]")), producer('mf'))

    				// `matching` function tests parameter
    				// against passed regular expression.
    				parameter 'offset': value(consumer(matching("[0-9]+")), producer(123))

    				// `notMatching` functions tests if parameter
    				// does not match passed regular expression.
    				parameter 'loginStartsWith': value(consumer(notMatching(".{0,2}")), producer(3))
    			}
    		}

    		//...
    	}

    	response {
    		//...
    	}
    }

It may contain additional request headers…​

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		//...

    		// Each header is added in form `'Header-Name' : 'Header-Value'`.
    		// there are also some helper methods
    		headers {
    			header 'key': 'value'
    			contentType(applicationJson())
    		}

    		//...
    	}

    	response {
    		//...
    	}
    }

…​and a request body.

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		//...

    		// Currently only JSON format of request body is supported.
    		// Format will be determined from a header or body's content.
    		body '''{ "login" : "john", "name": "John The Contract" }'''
    	}

    	response {
    		//...
    	}
    }

#### Response

Minimal response must contain HTTP status code.

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		//...
    	}
    	response {
    		// Status code sent by the server
    		// in response to request specified above.
    		status 200
    	}
    }

Besides status response may contain headers and body, which are specified the same way as in the request (see previous paragraph).

#### Dynamic properties

The contract can contain some dynamic properties - timestamps / ids etc. You don’t want to enforce the consumers to stub their clocks to always return the same value of time so that it gets matched by the stub. That’s why we allow you to provide the dynamic parts in your contracts in two ways. One is to pass them directly in the body and one to set them in a separate section called `testMatchers` and `stubMatchers`.

##### Dynamic properties inside the body

You can set the properties inside the body either via the `value` method

    value(consumer(...), producer(...))
    value(c(...), p(...))
    value(stub(...), test(...))
    value(client(...), server(...))

or if you’re using the Groovy map notation for body you can use the `$()` method

    $(consumer(...), producer(...))
    $(c(...), p(...))
    $(stub(...), test(...))
    $(client(...), server(...))

All of the aforementioned approaches are equal. That means that `stub` and `client` methods are aliases over the `consumer` method. Let’s take a closer look at what we can do with those values in the subsequent sections.

###### Regular expressions

You can use regular expressions to write your requests in Contract DSL. It is particularly useful when you want to indicate that a given response should be provided for requests that follow a given pattern. Also, you can use it when you need to use patterns and not exact values both for your test and your server side tests.

Please see the example below:

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		method('GET')
    		url $(consumer(~/\/[0-9]{2}/), producer('/12'))
    	}
    	response {
    		status 200
    		body(
    				id: $(anyNumber()),
    				surname: $(
    						consumer('Kowalsky'),
    						producer(regex('[a-zA-Z]+'))
    				),
    				name: 'Jan',
    				created: $(consumer('2014-02-02 12:23:43'), producer(execute('currentDate(it)'))),
    				correlationId: value(consumer('5d1f9fef-e0dc-4f3d-a7e4-72d2220dd827'),
    						producer(regex('[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}'))
    				)
    		)
    		headers {
    			header 'Content-Type': 'text/plain'
    		}
    	}
    }

You can also provide only one side of the communication using a regular expression. If you do that then automatically we’ll provide the generated string that matches the provided regular expression. For example:

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		method 'PUT'
    		url value(consumer(regex('/foo/[0-9]{5}')))
    		body([
    			requestElement: $(consumer(regex('[0-9]{5}')))
    		])
    		headers {
    			header('header', $(consumer(regex('application\\/vnd\\.fraud\\.v1\\+json;.*'))))
    		}
    	}
    	response {
    		status 200
    		body([
    			responseElement: $(producer(regex('[0-9]{7}')))
    		])
    		headers {
    			contentType("application/vnd.fraud.v1+json")
    		}
    	}
    }

In this example for request and response the opposite side of the communication will have the respective data generated.

Spring Cloud Contract comes with a series of predefined regular expressions that you can use in your contracts.

    protected static final Pattern TRUE_OR_FALSE = Pattern.compile(/(true|false)/)
    protected static final Pattern ONLY_ALPHA_UNICODE = Pattern.compile(/[\p{L}]*/)
    protected static final Pattern NUMBER = Pattern.compile('-?\\d*(\\.\\d+)?')
    protected static final Pattern IP_ADDRESS = Pattern.compile('([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])')
    protected static final Pattern HOSTNAME_PATTERN = Pattern.compile('((http[s]?|ftp):\\/)\\/?([^:\\/\\s]+)(:[0-9]{1,5})?')
    protected static final Pattern EMAIL = Pattern.compile('[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,4}');
    protected static final Pattern URL = Pattern.compile('((www\\.|(http|https|ftp|news|file)+\\:\\/\\/)[_.a-z0-9-]+\\.[a-z0-9\\/_:@=.+?,##%&~-]*[^.|\\\'|\\# |!|\\(|?|,| |>|<|;|\\)])')
    protected static final Pattern UUID = Pattern.compile('[a-z0-9]{8}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{12}')
    protected static final Pattern ANY_DATE = Pattern.compile('(\\d\\d\\d\\d)-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])')
    protected static final Pattern ANY_DATE_TIME = Pattern.compile('([0-9]{4})-(1[0-2]|0[1-9])-(3[01]|0[1-9]|[12][0-9])T(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])')
    protected static final Pattern ANY_TIME = Pattern.compile('(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])')

    String onlyAlphaUnicode() {
    	return ONLY_ALPHA_UNICODE.pattern()
    }

    String number() {
    	return NUMBER.pattern()
    }

    String anyBoolean() {
    	return TRUE_OR_FALSE.pattern()
    }

    String ipAddress() {
    	return IP_ADDRESS.pattern()
    }

    String hostname() {
    	return HOSTNAME_PATTERN.pattern()
    }

    String email() {
    	return EMAIL.pattern()
    }

    String url() {
    	return URL.pattern()
    }

    String uuid(){
    	return UUID.pattern()
    }

    String isoDate() {
    	return ANY_DATE.pattern()
    }

    String isoDateTime() {
    	return ANY_DATE_TIME.pattern()
    }

    String isoTime() {
    	return ANY_TIME.pattern()
    }

so in your contract you can use it like this

    Contract dslWithOptionalsInString = Contract.make {
    	priority 1
    	request {
    		method 'POST'
    		url '/users/password'
    		headers {
    			contentType(applicationJson())
    		}
    		body(
    				email: $(consumer(optional(regex(email()))), producer('abc@abc.com')),
    				callback_url: $(consumer(regex(hostname())), producer('http://partners.com'))
    		)
    	}
    	response {
    		status 404
    		headers {
    			contentType(applicationJson())
    		}
    		body(
    				code: value(consumer("123123"), producer(optional("123123"))),
    				message: "User not found by email = [${value(producer(regex(email())), consumer('not.existing@user.com'))}]"
    		)
    	}
    }

###### Passing optional parameters

It is possible to provide optional parameters in your contract. It’s only possible to have optional parameter for the:

- STUB side of the Request

- TEST side of the Response

Example:

    org.springframework.cloud.contract.spec.Contract.make {
    	priority 1
    	request {
    		method 'POST'
    		url '/users/password'
    		headers {
    			contentType(applicationJson())
    		}
    		body(
    				email: $(consumer(optional(regex(email()))), producer('abc@abc.com')),
    				callback_url: $(consumer(regex(hostname())), producer('http://partners.com'))
    		)
    	}
    	response {
    		status 404
    		headers {
    			header 'Content-Type': 'application/json'
    		}
    		body(
    				code: value(consumer("123123"), producer(optional("123123")))
    		)
    	}
    }

By wrapping a part of the body with the `optional()` method you are in fact creating a regular expression that should be present 0 or more times.

That way for the example above the following test would be generated if you pick Spock:

    """
     given:
      def request = given()
        .header("Content-Type", "application/json")
        .body('''{"email":"abc@abc.com","callback_url":"http://partners.com"}''')

     when:
      def response = given().spec(request)
        .post("/users/password")

     then:
      response.statusCode == 404
      response.header('Content-Type')  == 'application/json'
     and:
      DocumentContext parsedJson = JsonPath.parse(response.body.asString())
      assertThatJson(parsedJson).field("code").matches("(123123)?")
    """

and the following stub:

    '''
    {
      "request" : {
        "url" : "/users/password",
        "method" : "POST",
        "bodyPatterns" : [ {
          "matchesJsonPath" : "$[?(@.email =~ /([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\\\.[a-zA-Z]{2,4})?/)]"
        }, {
          "matchesJsonPath" : "$[?(@.callback_url =~ /((http[s]?|ftp):\\\\/)\\\\/?([^:\\\\/\\\\s]+)(:[0-9]{1,5})?/)]"
        } ],
        "headers" : {
          "Content-Type" : {
            "equalTo" : "application/json"
          }
        }
      },
      "response" : {
        "status" : 404,
        "body" : "{\\"code\\":\\"123123\\",\\"message\\":\\"User not found by email == [not.existing@user.com]\\"}",
        "headers" : {
          "Content-Type" : "application/json"
        }
      },
      "priority" : 1
    }
    '''

###### Executing custom methods on server side

It is also possible to define a method call to be executed on the server side during the test. Such a method can be added to the class defined as "baseClassForTests" in the configuration. Example:

Contract

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		method 'PUT'
    		url $(consumer(regex('^/api/[0-9]{2}$')), producer('/api/12'))
    		headers {
    			header 'Content-Type': 'application/json'
    		}
    		body '''\
    				[{
    					"text": "Gonna see you at Warsaw"
    				}]
    			'''
    	}
    	response {
    		body (
    				path: $(consumer('/api/12'), producer(regex('^/api/[0-9]{2}$'))),
    				correlationId: $(consumer('1223456'), producer(execute('isProperCorrelationId($it)')))
    		)
    		status 200
    	}
    }

Base class

    abstract class BaseMockMvcSpec extends Specification {

    	def setup() {
    		RestAssuredMockMvc.standaloneSetup(new PairIdController())
    	}

    	void isProperCorrelationId(Integer correlationId) {
    		assert correlationId == 123456
    	}

    	void isEmpty(String value) {
    		assert value == null
    	}

    }

Important | You can’t use both a String and `execute` to perform concatenation. E.g. calling `header('Authorization', 'Bearer ' + execute('authToken()'))` will lead to improper results. To make this work just call `header('Authorization', execute('authToken()'))` and ensure that the `authToken()` method returns everything that you need.

##### Dynamic properties in matchers sections

If you’ve been working with Pact this might seem familiar. Quite a few users are used to having a separation between the body and setting dynamic parts of your contract.

That’s why you can profit from two separate sections. One is called `stubMatchers` where you can define the dynamic values that should end up in a stub. You can set it in the `request` or `inputMessage` part of your contract. The other is called `testMatchers` which is present in the `response` or `outputMessage` side of the contract.

Currently we support only JSON Path based matchers with the following matching possibilities. For `stubMatchers`:

- `byEquality()` - the value taken from the response via the provided JSON Path needs to be equal to the provided value in the contract

- `byRegex(…​)` - the value taken from the response via the provided JSON Path needs to match the regex

- `byDate()` - the value taken from the response via the provided JSON Path needs to match the regex for ISO Date

- `byTimestamp()` - the value taken from the response via the provided JSON Path needs to match the regex for ISO DateTime

- `byTime()` - the value taken from the response via the provided JSON Path needs to match the regex for ISO Time

For `testMatchers`:

- `byEquality()` - the value taken from the response via the provided JSON Path needs to be equal to the provided value in the contract

- `byRegex(…​)` - the value taken from the response via the provided JSON Path needs to match the regex

- `byDate()` - the value taken from the response via the provided JSON Path needs to match the regex for ISO Date

- `byTimestamp()` - the value taken from the response via the provided JSON Path needs to match the regex for ISO DateTime

- `byTime()` - the value taken from the response via the provided JSON Path needs to match the regex for ISO Time

- `byType()` - the value taken from the response via the provided JSON Path needs to be of the same type as the type defined in the body of the response in the contract. `byType` can take a closure where you can set `minOccurrence` and `maxOccurrence`. That way you can assert on the size of the collection.

- `byCommand(…​)` - the value taken from the response via the provided JSON Path will be passed as an input to the custom method that you’re providing. E.g. `byCommand('foo($it)')` will result in calling a `foo` method to which the value matching the JSON Path will get passed.

Let’s take a look at the following example:

    Contract contractDsl = Contract.make {
    	request {
    		method 'GET'
    		urlPath '/get'
    		body([
    				duck: 123,
    				alpha: "abc",
    				number: 123,
    				aBoolean: true,
    				date: "2017-01-01",
    				dateTime: "2017-01-01T01:23:45",
    				time: "01:02:34",
    				valueWithoutAMatcher: "foo",
    				valueWithTypeMatch: "string"
    		])
    		stubMatchers {
    			jsonPath('$.duck', byRegex("[0-9]{3}"))
    			jsonPath('$.duck', byEquality())
    			jsonPath('$.alpha', byRegex(onlyAlphaUnicode()))
    			jsonPath('$.alpha', byEquality())
    			jsonPath('$.number', byRegex(number()))
    			jsonPath('$.aBoolean', byRegex(anyBoolean()))
    			jsonPath('$.date', byDate())
    			jsonPath('$.dateTime', byTimestamp())
    			jsonPath('$.time', byTime())
    		}
    		headers {
    			contentType(applicationJson())
    		}
    	}
    	response {
    		status 200
    		body([
    				duck: 123,
    				alpha: "abc",
    				number: 123,
    				aBoolean: true,
    				date: "2017-01-01",
    				dateTime: "2017-01-01T01:23:45",
    				time: "01:02:34",
    				valueWithoutAMatcher: "foo",
    				valueWithTypeMatch: "string",
    				valueWithMin: [
    					1,2,3
    				],
    				valueWithMax: [
    					1,2,3
    				],
    				valueWithMinMax: [
    					1,2,3
    				],
    				valueWithMinEmpty: [],
    				valueWithMaxEmpty: [],
    		])
    		testMatchers {
    			// asserts the jsonpath value against manual regex
    			jsonPath('$.duck', byRegex("[0-9]{3}"))
    			// asserts the jsonpath value against the provided value
    			jsonPath('$.duck', byEquality())
    			// asserts the jsonpath value against some default regex
    			jsonPath('$.alpha', byRegex(onlyAlphaUnicode()))
    			jsonPath('$.alpha', byEquality())
    			jsonPath('$.number', byRegex(number()))
    			jsonPath('$.aBoolean', byRegex(anyBoolean()))
    			// asserts vs inbuilt time related regex
    			jsonPath('$.date', byDate())
    			jsonPath('$.dateTime', byTimestamp())
    			jsonPath('$.time', byTime())
    			// asserts that the resulting type is the same as in response body
    			jsonPath('$.valueWithTypeMatch', byType())
    			jsonPath('$.valueWithMin', byType {
    				// results in verification of size of array (min 1)
    				minOccurrence(1)
    			})
    			jsonPath('$.valueWithMax', byType {
    				// results in verification of size of array (max 3)
    				maxOccurrence(3)
    			})
    			jsonPath('$.valueWithMinMax', byType {
    				// results in verification of size of array (min 1 & max 3)
    				minOccurrence(1)
    				maxOccurrence(3)
    			})
    			jsonPath('$.valueWithMinEmpty', byType {
    				// results in verification of size of array (min 0)
    				minOccurrence(0)
    			})
    			jsonPath('$.valueWithMaxEmpty', byType {
    				// results in verification of size of array (max 0)
    				maxOccurrence(0)
    			})
    			// will execute a method `assertThatValueIsANumber`
    			jsonPath('$.duck', byCommand('assertThatValueIsANumber($it)'))
    		}
    		headers {
    			contentType(applicationJson())
    		}
    	}
    }

In this example we’re providing the dynamic portions of the contract in the matchers sections. For the request part you can see that for all fields but `valueWithoutAMatcher` we’re setting explicitly the values of regular expressions we’d like the stub to contain. For the `valueWithoutAMatcher` the verification will take place in the same way as without the usage of matchers - the test will perform an equality check in this case.

For the response side in the `testMatchers` section we’re defining all the dynamic parts in a similar manner. The only difference is that we have the `byType` matchers too. In that case we’re checking 4 fields in the way that we’re verifying whether the response from the test has a value whose JSON path matching the given field is of the same type as the one defined in the response body and:

- for `$.valueWithTypeMatch` - we’re just checking the whether the type is the same

- for `$.valueWithMin` - we’re checking the type and assert if the size is greater or equal to the min occurrence

- for `$.valueWithMax` - we’re checking the type and assert if the size is smaller or equal to the max occurrence

- for `$.valueWithMinMax` - we’re checking the type and assert if the size is between the min and max occurrence

The resulting test would look more or less like this (note that we’re separating the autogenerated assertions and the one from matchers with an `and` section):

    // given:
     MockMvcRequestSpecification request = given()
       .header("Content-Type", "application/json")
       .body("{\"duck\":123,\"alpha\":\"abc\",\"number\":123,\"aBoolean\":true,\"date\":\"2017-01-01\",\"dateTime\":\"2017-01-01T01:23:45\",\"time\":\"01:02:34\",\"valueWithoutAMatcher\":\"foo\",\"valueWithTypeMatch\":\"string\"}");

    // when:
     ResponseOptions response = given().spec(request)
       .get("/get");

    // then:
     assertThat(response.statusCode()).isEqualTo(200);
     assertThat(response.header("Content-Type")).matches("application/json.*");
    // and:
     DocumentContext parsedJson = JsonPath.parse(response.getBody().asString());
     assertThatJson(parsedJson).field("valueWithoutAMatcher").isEqualTo("foo");
    // and:
     assertThat(parsedJson.read("$.duck", String.class)).matches("[0-9]{3}");
     assertThat(parsedJson.read("$.duck", Integer.class)).isEqualTo(123);
     assertThat(parsedJson.read("$.alpha", String.class)).matches("[\\p{L}]*");
     assertThat(parsedJson.read("$.alpha", String.class)).isEqualTo("abc");
     assertThat(parsedJson.read("$.number", String.class)).matches("-?\\d*(\\.\\d+)?");
     assertThat(parsedJson.read("$.aBoolean", String.class)).matches("(true|false)");
     assertThat(parsedJson.read("$.date", String.class)).matches("(\\d\\d\\d\\d)-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])");
     assertThat(parsedJson.read("$.dateTime", String.class)).matches("([0-9]{4})-(1[0-2]|0[1-9])-(3[01]|0[1-9]|[12][0-9])T(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])");
     assertThat(parsedJson.read("$.time", String.class)).matches("(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])");
     assertThat((Object) parsedJson.read("$.valueWithTypeMatch")).isInstanceOf(java.lang.String.class);
     assertThat((Object) parsedJson.read("$.valueWithMin")).isInstanceOf(java.util.List.class);
     assertThat(parsedJson.read("$.valueWithMin", java.util.Collection.class).size()).isGreaterThanOrEqualTo(1);
     assertThat((Object) parsedJson.read("$.valueWithMax")).isInstanceOf(java.util.List.class);
     assertThat(parsedJson.read("$.valueWithMax", java.util.Collection.class).size()).isLessThanOrEqualTo(3);
     assertThat((Object) parsedJson.read("$.valueWithMinMax")).isInstanceOf(java.util.List.class);
     assertThat(parsedJson.read("$.valueWithMinMax", java.util.Collection.class).size()).isBetween(1, 3);
     assertThat((Object) parsedJson.read("$.valueWithMinEmpty")).isInstanceOf(java.util.List.class);
     assertThat(parsedJson.read("$.valueWithMinEmpty", java.util.Collection.class).size()).isGreaterThanOrEqualTo(0);
     assertThat((Object) parsedJson.read("$.valueWithMaxEmpty")).isInstanceOf(java.util.List.class);
     assertThat(parsedJson.read("$.valueWithMaxEmpty", java.util.Collection.class).size()).isLessThanOrEqualTo(0);
     assertThatValueIsANumber(parsedJson.read("$.duck"));

and the WireMock stub like this:

    				'''
    {
      "request" : {
        "urlPath" : "/get",
        "method" : "GET",
        "headers" : {
          "Content-Type" : {
            "matches" : "application/json.*"
          }
        },
        "bodyPatterns" : [ {
          "matchesJsonPath" : "$[?(@.valueWithoutAMatcher == 'foo')]"
        }, {
          "matchesJsonPath" : "$[?(@.valueWithTypeMatch == 'string')]"
        }, {
          "matchesJsonPath" : "$.list.some.nested[?(@.anothervalue == 4)]"
        }, {
          "matchesJsonPath" : "$.list.someother.nested[?(@.anothervalue == 4)]"
        }, {
          "matchesJsonPath" : "$.list.someother.nested[?(@.json == 'with value')]"
        }, {
          "matchesJsonPath" : "$[?(@.duck =~ /([0-9]{3})/)]"
        }, {
          "matchesJsonPath" : "$[?(@.duck == 123)]"
        }, {
          "matchesJsonPath" : "$[?(@.alpha =~ /([\\\\p{L}]*)/)]"
        }, {
          "matchesJsonPath" : "$[?(@.alpha == 'abc')]"
        }, {
          "matchesJsonPath" : "$[?(@.number =~ /(-?\\\\d*(\\\\.\\\\d+)?)/)]"
        }, {
          "matchesJsonPath" : "$[?(@.aBoolean =~ /((true|false))/)]"
        }, {
          "matchesJsonPath" : "$[?(@.date =~ /((\\\\d\\\\d\\\\d\\\\d)-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01]))/)]"
        }, {
          "matchesJsonPath" : "$[?(@.dateTime =~ /(([0-9]{4})-(1[0-2]|0[1-9])-(3[01]|0[1-9]|[12][0-9])T(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9]))/)]"
        }, {
          "matchesJsonPath" : "$[?(@.time =~ /((2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9]))/)]"
        }, {
          "matchesJsonPath" : "$.list.some.nested[?(@.json =~ /(.*)/)]"
        } ]
      },
      "response" : {
        "status" : 200,
        "body" : "{\\"duck\\":123,\\"alpha\\":\\"abc\\",\\"number\\":123,\\"aBoolean\\":true,\\"date\\":\\"2017-01-01\\",\\"dateTime\\":\\"2017-01-01T01:23:45\\",\\"time\\":\\"01:02:34\\",\\"valueWithoutAMatcher\\":\\"foo\\",\\"valueWithTypeMatch\\":\\"string\\",\\"valueWithMin\\":[1,2,3],\\"valueWithMax\\":[1,2,3],\\"valueWithMinMax\\":[1,2,3]}",
        "headers" : {
          "Content-Type" : "application/json"
        }
      }
    }
    '''

#### JAX-RS support

Starting with release 0.8.0 we support JAX-RS 2 Client API. Base class needs to define `protected WebTarget webTarget` and server initialization, right now the only option how to test JAX-RS API is to start a web server.

Request with a body needs to have a content type set otherwise `application/octet-stream` is going to be used.

In order to use JAX-RS mode, use the following settings:

    testMode === 'JAXRSCLIENT'

Example of a test API generated:

    '''
     // when:
      Response response = webTarget
        .path("/users")
        .queryParam("limit", "10")
        .queryParam("offset", "20")
        .queryParam("filter", "email")
        .queryParam("sort", "name")
        .queryParam("search", "55")
        .queryParam("age", "99")
        .queryParam("name", "Denis.Stepanov")
        .queryParam("email", "bob@email.com")
        .request()
        .method("GET");

      String responseAsString = response.readEntity(String.class);

     // then:
      assertThat(response.getStatus()).isEqualTo(200);
     // and:
      DocumentContext parsedJson = JsonPath.parse(responseAsString);
      assertThatJson(parsedJson).field("property1").isEqualTo("a");
    '''

#### Async support

If you’re using asynchronous communication on the server side (your controllers are returning `Callable`, `DeferredResult` etc. then inside your contract you have to provide in the `response` section a `async()` method. Example:

    org.springframework.cloud.contract.spec.Contract.make {
        request {
            method 'GET'
            url '/get'
        }
        response {
            status 200
            body 'Passed'
            async()
        }
    }

#### Working with Context Paths

Spring Cloud Contract supports context paths.

Important | The only thing that changes in order to fully support context paths is the switch on the PRODUCER side. The autogenerated tests need to be using the EXPLICIT mode.

The consumer side remains untouched, in order for the generated test to pass you have to switch the EXPLICIT mode.

Maven

    <plugin>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-contract-maven-plugin</artifactId>
        <version>${spring-cloud-contract.version}</version>
        <extensions>true</extensions>
        <configuration>
            <testMode>EXPLICIT</testMode>
        </configuration>
    </plugin>

Gradle

    contracts {
    		testMode = 'EXPLICIT'
    }

That way you’ll generate a test that DOES NOT use MockMvc. It means that you’re generating real requests and you need to setup your generated test’s base class to work on a real socket.

Let’s imagine the following contract:

    org.springframework.cloud.contract.spec.Contract.make {
    	request {
    		method 'GET'
    		url '/my-context-path/url'
    	}
    	response {
    		status 200
    	}
    }

Here is an example of how to set up a base class and Rest Assured for everything to work correctly.

    import com.jayway.restassured.RestAssured;
    import org.junit.Before;
    import org.springframework.boot.context.embedded.LocalServerPort;
    import org.springframework.boot.test.context.SpringBootTest;

    @SpringBootTest(classes = ContextPathTestingBaseClass.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
    class ContextPathTestingBaseClass {

    	@LocalServerPort int port;

    	@Before
    	public void setup() {
    		RestAssured.baseURI = "http://localhost";
    		RestAssured.port = this.port;
    	}
    }

That way all:

- all your requests in the autogenerated tests will be sent to the real endpoint with your context path included (e.g. `/my-context-path/url`)

- your contracts reflect that you have a context path, thus your generated stubs will also have that information (e.g. in the stubs you’ll see that you have too call `/my-context-path/url`)

#### Messaging Top-Level Elements

The DSL for messaging looks a little bit different than the one that focuses on HTTP.

##### Output triggered by a method

The output message can be triggered by calling a method (e.g. a Scheduler was started and a message was sent)

    def dsl = Contract.make {
    	// Human readable description
    	description 'Some description'
    	// Label by means of which the output message can be triggered
    	label 'some_label'
    	// input to the contract
    	input {
    		// the contract will be triggered by a method
    		triggeredBy('bookReturnedTriggered()')
    	}
    	// output message of the contract
    	outputMessage {
    		// destination to which the output message will be sent
    		sentTo('output')
    		// the body of the output message
    		body('''{ "bookName" : "foo" }''')
    		// the headers of the output message
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

In this case the output message will be sent to `output` if a method called `bookReturnedTriggered` will be executed. In the message publisher’s side we will generate a test that will call that method to trigger the message. On the consumer side you can use the `some_label` to trigger the message.

##### Output triggered by a message

The output message can be triggered by receiving a message.

    def dsl = Contract.make {
    	description 'Some Description'
    	label 'some_label'
    	// input is a message
    	input {
    		// the message was received from this destination
    		messageFrom('input')
    		// has the following body
    		messageBody([
    		        bookName: 'foo'
    		])
    		// and the following headers
    		messageHeaders {
    			header('sample', 'header')
    		}
    	}
    	outputMessage {
    		sentTo('output')
    		body([
    		        bookName: 'foo'
    		])
    		headers {
    			header('BOOK-NAME', 'foo')
    		}
    	}
    }

In this case the output message will be sent to `output` if a proper message will be received on the `input` destination. In the message publisher’s side we will generate a test that will send the input message to the defined destination. On the consumer side you can either send a message to the input destination or use the `some_label` to trigger the message.

##### Consumer / Producer

In HTTP you have a notion of `client`/`stub and `server`/`test` notation. You can use them also in messaging but we’re providing also the `consumer` and `produer` methods as presented below (note you can use either `$` or `value` methods to provide `consumer` and `producer` parts)

    Contract.make {
    	label 'some_label'
    	input {
    		messageFrom value(consumer('jms:output'), producer('jms:input'))
    		messageBody([
    				bookName: 'foo'
    		])
    		messageHeaders {
    			header('sample', 'header')
    		}
    	}
    	outputMessage {
    		sentTo $(consumer('jms:input'), producer('jms:output'))
    		body([
    				bookName: 'foo'
    		])
    	}
    }

### Extending the DSL

It is possible to provide your own functions to the DSL. The key requirement for this feature was to maintain the static compatibility. Below you will be able to see an example of:

- creation of a JAR with reusable classes

- referencing of these classes in the DSLs

The full example can be found here.

#### Common JAR

Below you can find three classes that we will reuse in the DSLs.

PatternUtils contains functions used by both the consumer and the producer.

    package com.example;

    import java.util.regex.Pattern;

    /**
     * If you want to use {@link Pattern} directly in your tests
     * then you can create a class resembling this one. It can
     * contain all the {@link Pattern} you want to use in the DSL.
     *
     * <pre>
     * {@code
     * request {
     *     body(
     *         [ age: $(c(PatternUtils.oldEnough()))]
     *     )
     * }
     * </pre>
     *
     * Notice that we're using both {@code $()} for dynamic values
     * and {@code c()} for the consumer side.
     *
     * @author Marcin Grzejszczak
     */
    public class PatternUtils {
    	public static String tooYoung() {
    		return "[0-1][0-9]";
    	}

    	public static Pattern oldEnough() {
    		return Pattern.compile("[2-9][0-9]");
    	}

    	public static Pattern anyName() {
    		return Pattern.compile("[a-zA-Z]+");
    	}

    	/**
    	 * Makes little sense but it's just an example ;)
    	 */
    	public static Pattern ok() {
    		return Pattern.compile("OK");
    	}
    }

ConsumerUtils contains functions used by the consumer.

    package com.example;

    import org.springframework.cloud.contract.spec.internal.ClientDslProperty;
    import org.springframework.cloud.contract.spec.internal.DslProperty;

    /**
     * DSL Properties passed to the DSL from the consumer's perspective.
     * That means that on the input side {@code Request} for HTTP
     * or {@code Input} for messaging you can have a regular expression.
     * On the {@code Response} for HTTP or {@code Output} for messaging
     * you have to have a concrete value.
     *
     * @author Marcin Grzejszczak
     */
    public class ConsumerUtils {
    	/**
    	 * Consumer side property. By using the {@link ClientDslProperty}
    	 * you can omit most of boilerplate code from the perspective
    	 * of dynamic values. Example
    	 *
    	 * <pre>
    	 * {@code
    	 * request {
    	 *     body(
    	 *         [ age: $(ConsumerUtils.oldEnough())]
    	 *     )
    	 * }
    	 * </pre>
    	 *
    	 * That way the consumer side value of age field will be
    	 * a regular expression and the producer side will be generated.
    	 *
    	 * @author Marcin Grzejszczak
    	 */
    	public static ClientDslProperty oldEnough() {
    		return new ClientDslProperty(PatternUtils.oldEnough());
    	}

    	/**
    	 * Consumer side property. By using the {@link ClientDslProperty}
    	 * you can omit most of boilerplate code from the perspective
    	 * of dynamic values. Example
    	 *
    	 * <pre>
    	 * {@code
    	 * request {
    	 *     body(
    	 *         [ name: $(ConsumerUtils.anyName())]
    	 *     )
    	 * }
    	 * </pre>
    	 *
    	 * That way the consumer will be a regular expression and the
    	 * producer side value will be equal to {@code marcin}
    	 */
    	public static DslProperty anyName() {
    		return new DslProperty<>(PatternUtils.anyName(), "marcin");
    	}
    }

ProducerUtils contains functions used by the producer.

    package com.example;

    import org.springframework.cloud.contract.spec.internal.ServerDslProperty;

    /**
     * DSL Properties passed to the DSL from the producer's perspective.
     * That means that on the input side {@code Request} for HTTP
     * or {@code Input} for messaging you have to have a concrete value.
     * On the {@code Response} for HTTP or {@code Output} for messaging
     * you can have a regular expression.
     *
     * @author Marcin Grzejszczak
     */
    public class ProducerUtils {

    	/**
    	 * Producer side property. By using the {@link ProducerUtils}
    	 * you can omit most of boilerplate code from the perspective
    	 * of dynamic values. Example
    	 *
    	 * <pre>
    	 * {@code
    	 * response {
    	 *     body(
    	 *         [ status: $(ProducerUtils.ok())]
    	 *     )
    	 * }
    	 * </pre>
    	 *
    	 * That way the producer side value of age field will be
    	 * a regular expression and the consumer side will be generated.
    	 */
    	public static ServerDslProperty ok() {
    		return new ServerDslProperty(PatternUtils.ok());
    	}
    }

#### Adding the dependency to project

In order for the plugins and IDE to be able to reference the common JAR classes you need to pass the dependency to your project.

##### Test dependency in project’s dependencies

First add the common jar dependency as a test dependency. That way since your contracts files are available at test resources path, automatically the common jar classes will be visible in your Groovy files.

Maven

    <dependency>
    	<groupId>com.example</groupId>
    	<artifactId>beer-common</artifactId>
    	<version>${project.version}</version>
    	<scope>test</scope>
    </dependency>

Gradle

    testCompile("com.example:beer-common:0.0.1-SNAPSHOT")

##### Test dependency in plugin’s dependencies

Now you have to add the dependency for the plugin to reuse at runtime.

Maven

    <plugin>
    	<groupId>org.springframework.cloud</groupId>
    	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
    	<version>${spring-cloud-contract.version}</version>
    	<extensions>true</extensions>
    	<configuration>
    		<packageWithBaseClasses>com.example</packageWithBaseClasses>
    	</configuration>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-contract-verifier</artifactId>
    			<version>${spring-cloud-contract.version}</version>
    		</dependency>
    		<dependency>
    			<groupId>com.example</groupId>
    			<artifactId>beer-common</artifactId>
    			<version>${project.version}</version>
    			<scope>compile</scope>
    		</dependency>
    	</dependencies>
    </plugin>

Gradle

    classpath "com.example:beer-common:0.0.1-SNAPSHOT"

##### Referencing classes in DSLs

Now you can reference your classes in your DSL. Example:

    package contracts.beer.rest

    import org.springframework.cloud.contract.spec.Contract

    import static com.example.ConsumerUtils.oldEnough
    import static com.example.ProducerUtils.ok

    Contract.make {
    	request {
    		description("""
    Represents a successful scenario of getting a beer

    given:
    	client is old enough
    when:
    	he applies for a beer
    then:
    	we'll grant him the beer
    """)
    		method 'POST'
    		url '/check'
    		body(
    				age: $(oldEnough())
    		)
    		headers {
    			contentType(applicationJson())
    		}
    	}
    	response {
    		status 200
    		body("""
    			{
    				"status": "${value(ok())}"
    			}
    			""")
    		headers {
    			contentType(applicationJson())
    		}
    	}
    }

### Links

Here you can find interesting links related to Spring Cloud Contract Verifier:

- Spring Cloud Contract Github Repository

- Spring Cloud Contract Samples

- Spring Cloud Contract Documentation

- Accurest Legacy Documentation

- Spring Cloud Contract Stub Runner Documentation

- Spring Cloud Contract Stub Runner Messaging Documentation

- Spring Cloud Contract Gitter

- Spring Cloud Contract Maven Plugin