Spring Cloud Contract


Table of Contents

1. Spring Cloud Contract
2. Spring Cloud Contract Verifier Introduction
2.1. Why a Contract Verifier?
2.1.1. Testing issues
2.2. Purposes
2.3. How It Works
2.3.1. Defining the contract
2.3.2. Client Side
2.3.3. Server Side
2.4. Step-by-step Guide to Consumer Driven Contracts (CDC)
2.4.1. Technical note
2.4.2. Consumer side (Loan Issuance)
2.4.3. Producer side (Fraud Detection server)
2.4.4. Consumer Side (Loan Issuance) Final Step
2.5. Dependencies
2.6. Additional Links
2.6.1. Spring Cloud Contract video
2.6.2. Readings
2.7. Samples
3. Spring Cloud Contract FAQ
3.1. Why use Spring Cloud Contract Verifier and not X ?
3.2. What is this value(consumer(), producer()) ?
3.3. How to do Stubs versioning?
3.3.1. API Versioning
3.3.2. JAR versioning
3.3.3. Dev or prod stubs
3.4. Common repo with contracts
3.4.1. Repo structure
3.4.2. Workflow
3.4.3. Consumer
3.4.4. Producer
3.5. Can I have multiple base classes for tests?
3.6. How can I debug the request/response being sent by the generated tests client?
3.6.1. How can I debug the mapping/request/response being sent by WireMock?
3.6.2. How can I see what got registered in the HTTP server stub?
3.6.3. Can I reference the request from the response?
3.6.4. Can I reference text from file?
4. Spring Cloud Contract Verifier Setup
4.1. Gradle Project
4.1.1. Prerequisites
4.1.2. Add Gradle Plugin with Dependencies
4.1.3. Gradle and Rest Assured 2.0
4.1.4. Snapshot Versions for Gradle
4.1.5. Add stubs
4.1.6. Run the Plugin
4.1.7. Default Setup
4.1.8. Configure Plugin
4.1.9. Configuration Options
4.1.10. Single Base Class for All Tests
4.1.11. Different Base Classes for Contracts
4.1.12. Invoking Generated Tests
4.1.13. Spring Cloud Contract Verifier on the Consumer Side
4.2. Maven Project
4.2.1. Add maven plugin
4.2.2. Maven and Rest Assured 2.0
4.2.3. Snapshot versions for Maven
4.2.4. Add stubs
4.2.5. Run plugin
4.2.6. Configure plugin
4.2.7. Configuration Options
4.2.8. Single Base Class for All Tests
4.2.9. Different base classes for contracts
4.2.10. Invoking generated tests
4.2.11. Maven Plugin and STS
4.2.12. Spring Cloud Contract Verifier on the Consumer Side
4.3. Stubs and Transitive Dependencies
4.4. Scenarios
5. Spring Cloud Contract Verifier Messaging
5.1. Integrations
5.2. Manual Integration Testing
5.3. Publisher-Side Test Generation
5.3.1. Scenario 1: No Input Message
5.3.2. Scenario 2: Output Triggered by Input
5.3.3. Scenario 3: No Output Message
5.4. Consumer Stub Generation
6. Spring Cloud Contract Stub Runner
6.1. Snapshot versions
6.2. Publishing Stubs as JARs
6.3. Stub Runner Core
6.3.1. Retrieving stubs
Stub downloading
Classpath scanning
6.3.2. Running stubs
Limitations
Running using main app
HTTP Stubs
Viewing registered mappings
Messaging Stubs
6.4. Stub Runner JUnit Rule
6.4.1. Maven settings
6.4.2. Providing fixed ports
6.4.3. Fluent API
6.4.4. Stub Runner with Spring
6.5. Stub Runner Spring Cloud
6.5.1. Stubbing Service Discovery
Test profiles and service discovery
6.5.2. Additional Configuration
6.6. Stub Runner Boot Application
6.6.1. How to use it?
Stub Runner Server
Spring Cloud CLI
6.6.2. Endpoints
HTTP
Messaging
6.6.3. Example
6.6.4. Stub Runner Boot with Service Discovery
6.7. Stubs Per Consumer
6.8. Common
6.8.1. Common Properties for JUnit and Spring
6.8.2. Stub Runner Stubs IDs
7. Stub Runner for Messaging
7.1. Stub triggering
7.1.1. Trigger by Label
7.1.2. Trigger by Group and Artifact Ids
7.1.3. Trigger by Artifact Ids
7.1.4. Trigger All Messages
7.2. Stub Runner Integration
7.2.1. Adding the Runner to the Project
7.2.2. Disabling the functionality
Scenario 1 (no input message)
Scenario 2 (output triggered by input)
Scenario 3 (input with no output)
7.3. Stub Runner Stream
7.3.1. Adding the Runner to the Project
7.3.2. Disabling the functionality
Scenario 1 (no input message)
Scenario 2 (output triggered by input)
Scenario 3 (input with no output)
7.4. Stub Runner Spring AMQP
7.4.1. Adding the Runner to the Project
Triggering the message
Spring AMQP Test Configuration
8. Contract DSL
8.1. Limitations
8.2. Common Top-Level elements
8.2.1. Description
8.2.2. Name
8.2.3. Ignoring Contracts
8.2.4. Passing Values from Files
8.2.5. HTTP Top-Level Elements
8.3. Request
8.4. Response
8.5. Dynamic properties
8.5.1. Dynamic properties inside the body
8.5.2. Regular expressions
8.5.3. Passing Optional Parameters
8.5.4. Executing Custom Methods on the Server Side
8.5.5. Referencing the Request from the Response
8.5.6. Registering Your Own WireMock Extension
8.5.7. Dynamic Properties in the Matchers Sections
8.6. JAX-RS Support
8.7. Async Support
8.8. Working with Context Paths
8.9. Messaging Top-Level Elements
8.9.1. Output Triggered by a Method
8.9.2. Output Triggered by a Message
8.9.3. Consumer/Producer
8.9.4. Common
8.10. Multiple Contracts in One File
9. Customization
9.1. Extending the DSL
9.1.1. Common JAR
9.1.2. Adding the Dependency to the Project
9.1.3. Test the Dependency in the Project’s Dependencies
9.1.4. Test a Dependency in the Plugin’s Dependencies
9.1.5. Referencing classes in DSLs
10. Using the Pluggable Architecture
10.1. Custom Contract Converter
10.1.1. Pact Converter
10.1.2. Pact Contract
10.1.3. Pact for Producers
10.1.4. Pact for Consumers
10.2. Using the Custom Test Generator
10.3. Using the Custom Stub Generator
10.4. Using the Custom Stub Runner
10.5. Using the Custom Stub Downloader
11. Spring Cloud Contract WireMock
11.1. Registering Stubs Automatically
11.2. Using Files to Specify the Stub Bodies
11.3. Alternative: Using JUnit Rules
11.4. Relaxed SSL Validation for Rest Template
11.5. WireMock and Spring MVC Mocks
11.6. Customization of WireMock configuration
11.7. Generating Stubs using REST Docs
11.8. Generating Contracts by Using REST Docs
12. Migrations
12.1. 1.0.x → 1.1.x
12.1.1. New structure of generated stubs
12.2. 1.1.x → 1.2.x
12.2.1. Custom HttpServerStub
12.2.2. New packages for generated tests
12.2.3. New Methods in TemplateProcessor
12.2.4. RestAssured 3.0
12.3. 1.2.x → 2.0.x
12.3.1. No Camel support
13. Links

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

2.0.0.BUILD-SNAPSHOT

1. Spring Cloud Contract

You need confidence when pushing new features to a new application or service in a distributed system. This project provides support for Consumer Driven Contracts and service schemas in Spring applications (for both HTTP and message-based interactions), covering a range of options for writing tests, publishing them as assets, and asserting that a contract is kept by producers and consumers.

2. Spring Cloud Contract Verifier Introduction

[Tip]Tip

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

Spring Cloud Contract Verifier enables Consumer Driven Contract (CDC) development of JVM-based applications. It moves TDD to the level of software architecture.

Spring Cloud Contract Verifier ships with Contract Definition Language (CDL). Contract definitions are used to produce the 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, and test data is produced by Spring Cloud Contract Verifier.
  • Messaging routes, if you’re using a messaging service. We integrate with Spring Integration, Spring Cloud Stream, Spring AMQP, and Apache Camel. You can also set your own integrations.
  • Acceptance tests (in JUnit or Spock) are used to verify if server-side implementation of the API is compliant with the contract (server tests). A full test is generated by Spring Cloud Contract Verifier.

2.1 Why a Contract Verifier?

Assume that we have a system consisting of multiple microservices:

Microservices Architecture

2.1.1 Testing issues

If we wanted to test the application in top left corner to determine whether it can communicate with other services, 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.

Deploy all microservices and perform end to end tests

Advantages:

  • Simulates production.
  • Tests real communication between services.

Disadvantages:

  • To test one microservice, we have to deploy 6 microservices, a couple of databases, etc.
  • The environment where the tests run is locked for a single suite of tests (nobody else would be able to run the tests in the meantime).
  • They take a long time to run.
  • The feedback comes very late in the process.
  • They are extremely hard to debug.

Mock other microservices in unit/integration tests

Advantages:

  • They provide very fast feedback.
  • They have no infrastructure requirements.

Disadvantages:

  • The implementor of the service creates stubs that might have nothing to do with reality.
  • You can go to production with passing tests and failing production.

To solve the aforementioned issues, Spring Cloud Contract Verifier with Stub Runner was created. The 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 directly uses.

Stubbed Services

Spring Cloud Contract Verifier gives you the certainty that the stubs that you use 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 short, you can trust those stubs.

2.2 Purposes

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

  • To ensure that WireMock/Messaging stubs (used when developing the client) do exactly what the actual server-side implementation does.
  • 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 to be used on the server side.
[Important]Important

Spring Cloud Contract Verifier’s purpose is NOT to start writing business features in the contracts. 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 case and one for the negative case. Contract tests are used to test contracts between applications and not to simulate full behavior.

2.3 How It Works

This section explores how Spring Cloud Contract Verifier with Stub Runner works.

2.3.1 Defining the contract

As consumers of services, we need to define what exactly we want to achieve. We need to formulate our expectations. That is why we write contracts.

Assume that you want to send a request containing the ID of a client company and the amount it wants to borrow from us. You also want to send it to the /fraudcheck url via the PUT method.

package contracts

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

/*
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/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/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/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/json.*`
 */

2.3.2 Client Side

Spring Cloud Contract generates stubs, which you can use during client-side testing. You get a running WireMock instance/Messaging route that simulates the service. You would like to feed that instance with a proper stub definition.

At some point in time, you need to send a request to the Fraud Detection service.

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

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.

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

After that, during the tests, Spring Cloud Contract automatically finds the stubs (simulating the real service) in the Maven repository and exposes them on a configured (or random) port.

2.3.3 Server Side

Since you are developing your stub, you need to be sure that it actually resembles your concrete implementation. You cannot have a situation where your stub acts in one way and your application behaves in a different way, especially in production.

To ensure that your application behaves the way you define in your stub, tests are generated from the stub you provide.

The autogenerated test looks like this:

@Test
public void validate_shouldMarkClientAsFraud() throws Exception {
    // given:
        MockMvcRequestSpecification request = given()
                .header("Content-Type", "application/vnd.fraud.v1+json")
                .body("{\"client.id\":\"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("['rejection.reason']").isEqualTo("Amount too high");
}

2.4 Step-by-step Guide to Consumer Driven Contracts (CDC)

Consider an example of Fraud Detection and the Loan Issuance process. The business scenario is such that we want to issue loans to people but do not want them to steal from us. The current implementation of our system grants loans to everybody.

Assume that Loan Issuance is a client to the Fraud Detection server. In the current sprint, we must develop a new feature: if a client wants to borrow too much money, then we mark the client as a fraud.

Technical remark - Fraud Detection has an artifact-id of http-server, while Loan Issuance has an artifact-id of http-client, and both have a group-id of 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 code here.

[Tip]Tip

In this case, the producer owns the contracts. Physically, all the contract are in the producer’s repository.

2.4.1 Technical note

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

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

2.4.2 Consumer side (Loan Issuance)

As a developer of the Loan Issuance service (a consumer of the Fraud Detection server), you might do the following steps:

  1. Start doing TDD by writing a test for your feature.
  2. Write the missing implementation.
  3. Clone the Fraud Detection service repository locally.
  4. Define the contract locally in the repo of Fraud Detection service.
  5. Add the Spring Cloud Contract Verifier plugin.
  6. Run the integration tests.
  7. File a pull request.
  8. Create an initial implementation.
  9. Take over the pull request.
  10. Write the missing implementation.
  11. Deploy your app.
  12. Work online.

Start doing TDD by writing a test for 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");
}

Assume that you have written a test of your new feature. If a loan application for a big amount is received, the system 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. Assume that you need to send the request containing the ID of the client and the amount the client wants to borrow. You want 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, the port of the Fraud Detection service is set to 8080, and the application runs on 8090.

If you start the test at this point, it breaks, because no service currently runs on port 8080.

Clone the Fraud Detection service repository locally.

You can start by playing around with the server side contract. To do so, you must 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 a consumer, you need to define what exactly you want to achieve. You need to formulate your expectations. To do so, write the following contract:

[Important]Important

Place the contract under src/test/resources/contracts/fraud folder. The fraud folder is important because the producer’s test base class name references that folder.

package contracts

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

/*
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/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/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/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/json.*`
 */

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

[Tip]Tip

You must understand the map notation in order to set up contracts. Please read the Groovy docs regarding JSON.

The previously shown contract is an agreement between two sides that:

  • if an HTTP request is sent with all of

    • a PUT method on the /fraudcheck endpoint,
    • a JSON body with a client.id that matches the regular expression [0-9]{10} and loanAmount equal to 99999,
    • and a Content-Type header with a value of application/vnd.fraud.v1+json,
  • then an HTTP response is sent to the consumer that

    • has status 200,
    • contains a 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 you are ready to check the API in practice in the integration tests, you need to install the stubs locally.

Add the Spring Cloud Contract Verifier plugin.

We can add either a Maven or a Gradle plugin. In this example, you see how to add Maven. First, 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, add 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, you get the Spring Cloud Contract Verifier features which, from the provided contracts:

  • generate and run tests
  • produce and install stubs

You do not want to generate tests since you, as the consumer, want only to play with the stubs. You need to skip the test generation and execution. When you execute:

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

In the logs, you 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:1.5.5.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

The following 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 confirms 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 must do the following in your 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 the stubs of your collaborators. (Optional step) Because you’re playing with the collaborators offline, you can also provide the offline work switch.

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

Now, when you run your tests, you see something 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}]

This output means that Stub Runner has found your stubs and started a server for your 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 pull request.

What you have done until now is an iterative process. You can play around with the contract, install it locally, and work on the consumer side until the contract works as you wish.

Once you are satisfied with the results and the test passes, publish a pull request to the server side. Currently, the consumer side work is done.

2.4.3 Producer side (Fraud Detection server)

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

Create an initial implementation.

As a reminder, you can see the initial implementation here:

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

Take over the pull request.

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

You must 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, pass 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]Important

This example uses "convention based" naming by setting the packageWithBaseClasses property. Doing so means that the two last packages combine to make the name of the base test class. In our case, the contracts were placed under src/test/resources/contracts/fraud. Since you do not have two packages starting from the contracts folder, pick only one, which should be fraud. Add the Base suffix and capitalize fraud. That gives you the FraudBase test class name.

All the generated tests extend that class. Over there, you can set up your Spring Context or whatever is necessary. In this case, use Rest Assured MVC to start the server side FraudDetectionController.

package com.example.fraud;

import org.junit.Before;

import io.restassured.module.mockmvc.RestAssuredMockMvc;

public class FraudBase {
	@Before
	public void setup() {
		RestAssuredMockMvc.standaloneSetup(new FraudDetectionController(),
				new FraudStatsController(stubbedStatsProvider()));
	}

	private StatsProvider stubbedStatsProvider() {
		return fraudType -> {
			switch (fraudType) {
			case DRUNKS:
				return 100;
			case ALL:
				return 200;
			}
			return 0;
		};
	}

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

Now, if you run the ./mvnw clean install, you get something like this:

Results :

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

This error occurs because you have a new contract from which a test was generated and it failed since you have not implemented the feature. The auto-generated 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("{\"client.id\":\"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("['rejection.reason']").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.

Note that, on the producer side, you are also doing TDD. The expectations are expressed in the form of a test. This test sends a request to our own application with the URL, headers, and body defined in the contract. It also is expecting precisely defined values in the response. In other words, you have the red part of red, green, and refactor. It is time to convert the red into the green.

Write the missing implementation.

Because you know the expected input and expected output, you can write the missing implementation:

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

When you execute ./mvnw clean install again, the tests 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 finish your work, you can deploy your change. First, merge the branch:

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

Your CI might run something like ./mvnw clean deploy, which would publish both the application and the stub artifacts.

2.4.4 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 and indicate where the repository with your stubs is located. At this moment the stubs of the server side are automatically downloaded from Nexus/Artifactory. You can set the value of stubsMode to REMOTE. The following code shows an example of achieving the same thing by changing the properties.

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

That’s it!

2.5 Dependencies

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

For stub-runner, use spring-cloud-starter-stub-runner. When you use a plugin, add spring-cloud-starter-contract-verifier.

2.6 Additional Links

Here are some resources related to Spring Cloud Contract Verifier and Stub Runner. Note that some may be outdated, because the Spring Cloud Contract Verifier project is under constant development.

2.6.1 Spring Cloud Contract video

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

2.7 Samples

You can find some samples at samples.

3. Spring Cloud Contract FAQ

3.1 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

3.2 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]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]Important

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

3.3 How to do Stubs versioning?

3.3.1 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.

3.3.2 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"})

3.3.3 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.

3.4 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.

3.4.1 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>2.0.0.M6</version>
		<relativePath />
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<java.version>1.8</java.version>
		<spring-cloud-contract.version>2.0.0.BUILD-SNAPSHOT</spring-cloud-contract.version>
		<spring-cloud-dependencies.version>Finchley.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>

3.4.2 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.

3.4.3 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]Tip

You need to have Maven installed locally

3.4.4 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>
		<stubsMode>REMOTE</stubsMode>
		<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.

3.5 Can I have multiple base classes for tests?

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

3.6 How can I debug the request/response being sent by the generated tests client?

The generated tests all boil down to RestAssured in some form or fashion which relies on Apache HttpClient. HttpClient has a facility called wire logging which logs the entire request and response to HttpClient. Spring Boot has a logging common application property for doing this sort of thing, just add this to your application properties

logging.level.org.apache.http.wire=DEBUG

3.6.1 How can I debug the mapping/request/response being sent by WireMock?

Starting from version 1.2.0 we turn on WireMock logging to info and the WireMock notifier to being verbose. Now you will exactly know what request was received by WireMock server and which matching response definition was picked.

To turn off this feature just bump WireMock logging to ERROR

logging.level.com.github.tomakehurst.wiremock=ERROR

3.6.2 How can I see what got registered in the HTTP server stub?

You can use the mappingsOutputFolder property on @AutoConfigureStubRunner or StubRunnerRule to dump all mappings per artifact id. Also the port at which the given stub server was started will be attached.

3.6.3 Can I reference the request from the response?

Yes! With version 1.1.0 we’ve added such a possibility. On the HTTP stub server side we’re providing support for this for WireMock. In case of other HTTP server stubs you’ll have to implement the approach yourself.

3.6.4 Can I reference text from file?

Yes! With version 1.2.0 we’ve added such a possibility. It’s enough to call file(…​) method in the DSL and provide a path relative to where the contract lays.

4. Spring Cloud Contract Verifier Setup

You can set up Spring Cloud Contract Verifier in either of two ways

4.1 Gradle Project

To learn how to set up the Gradle project for Spring Cloud Contract Verifier, read the following sections:

4.1.1 Prerequisites

In order to use Spring Cloud Contract Verifier with WireMock, you muse use either a Gradle or a Maven plugin.

[Warning]Warning

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

4.1.2 Add Gradle Plugin with Dependencies

To add a Gradle plugin with dependencies, use code similar to this:

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'
}

4.1.3 Gradle and Rest Assured 2.0

By default, Rest Assured 3.x is added to the classpath. However, to use Rest Assured 2.x you can add it to the plugins classpath, as shown here:

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}"
		classpath "com.jayway.restassured:rest-assured:2.5.0"
		classpath "com.jayway.restassured:spring-mock-mvc:2.5.0"
	}
}

depenendencies {
    // all dependencies
    // you can exclude rest-assured from spring-cloud-contract-verifier
    testCompile "com.jayway.restassured:rest-assured:2.5.0"
    testCompile "com.jayway.restassured:spring-mock-mvc:2.5.0"
}

That way, the plugin automatically sees that Rest Assured 2.x is present on the classpath and modifies the imports accordingly.

4.1.4 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, as shown here:

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" }
	}
}

4.1.5 Add stubs

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

The directory containing stub definitions is treated as a class name, and each stub definition is treated as a single test. Spring Cloud Contract Verifier assumes that it contains at least one level of directories that are to be used as the test class name. If more than one level of nested directories is present, all except the last one is used as the package name. For example, with following structure:

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

Spring Cloud Contract Verifier creates a test class named defaultBasePackage.MyService with two methods:

  • shouldCreateUser()
  • shouldReturnUser()

4.1.6 Run the Plugin

The plugin registers itself to be invoked before a check task. If you want it to be part of your build process, you need to do nothing more. If you just want to generate tests, invoke the generateContractTests task.

4.1.7 Default Setup

The default Gradle Plugin setup creates the following Gradle part of the build (in 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
    contractRepository {
        cacheDownloadedContracts(true)
    }
}

tasks.create(type: Jar, name: 'verifierStubsJar', dependsOn: 'generateClientStubs') {
    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
        }
    }
}

4.1.8 Configure Plugin

To change the default configuration, add a contracts snippet to your Gradle config, as shown here:

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

4.1.9 Configuration Options

  • testMode: Defines the mode for acceptance tests. By default, the mode is MockMvc, which is based on Spring’s MockMvc. It can also be changed to JaxRsClient or to Explicit for real HTTP calls.
  • imports: Creates an array with imports that should be included in generated tests (for example ['org.myorg.Matchers']). By default, it creates an empty array.
  • staticImports: Creates an array with static imports that should be included in generated tests(for example ['org.myorg.Matchers.*']). By default, it creates an empty array.
  • basePackageForTests: Specifies the base package for all generated tests. If not set, the value is picked from baseClassForTests’s package and from `packageWithBaseClasses. If neither of these values are set, then the value is set to org.springframework.cloud.contract.verifier.tests.
  • baseClassForTests: Creates a base class for all generated tests. By default, if you use Spock classes, the class is spock.lang.Specification.
  • packageWithBaseClasses: Defines a package where all the base classes reside. This setting takes precedence over baseClassForTests.
  • baseClassMappings: Explicitly maps a contract package to a FQN of a base class. This setting takes precedence over packageWithBaseClasses and baseClassForTests.
  • ruleClassForTests: Specifies a rule that should be added to the generated test classes.
  • ignoredFiles: Uses an Antmatcher to allow defining stub files for which processing should be skipped. By default, it is an empty array.
  • contractsDslDir: Specifies the directory containing contracts written using the GroovyDSL. By default, its value is $rootDir/src/test/resources/contracts.
  • generatedTestSourcesDir: Specifies the test source directory where tests generated from the Groovy DSL should be placed. By default its value is $buildDir/generated-test-sources/contractVerifier.
  • stubsOutputDir: Specifies the directory where the generated WireMock stubs from the Groovy DSL should be placed.
  • targetFramework: Specifies 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 specify the location of the JAR containing the contracts: * contractDependency: Specifies the Dependency that provides groupid:artifactid:version:classifier coordinates. You can use the contractDependency closure to set it up. * contractsPath: Specifies the path to the jar. If contract dependencies are downloaded, the path defaults to groupid/artifactid where groupid is slash separated. Otherwise, it scans contracts under the provided directory. * contractsWorkOffline: Specifies whether to download the dependencies each time, so that you can work online. In other words, it specifies whether to reuses the local Maven repo.

4.1.10 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 an 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
	}

}

If you use Explicit mode, you can use a base class to initialize the whole tested app as you might see in regular integration tests. If you use the JAXRSCLIENT mode, this base class should also contain a protected WebTarget webTarget field. Right now, the only option to test the JAX-RS API is to start a web server.

4.1.11 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

By Convention

The convention is such that if you have a contract under (for example) src/test/resources/contract/foo/bar/baz/ and set the value of the packageWithBaseClasses property to com.example.base, then Spring Cloud Contract Verifier assumes that there is a BarBazBase class under the com.example.base package. In other words, the system takes the last two parts of the package, if they exist, and forms a class with a Base suffix. This rule takes precedence over baseClassForTests. Here is an example of how it works in the contracts closure:

packageWithBaseClasses = 'com.example.base'

By 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 called baseClassMappings that consists baseClassMapping objects that takes a contractPackageRegex to baseClassFQN mapping. Consider 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 did not succeed. (You could also provide the packageWithBaseClasses as a fallback.) That way, the tests generated from src/test/resources/contract/com/ contracts extend the com.example.ComBase, whereas the rest of the tests extend com.example.FooBase.

4.1.12 Invoking Generated Tests

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

./gradlew generateContractTests test

4.1.13 Spring Cloud Contract Verifier on the Consumer Side

In a consuming service, you need to configure the Spring Cloud Contract Verifier plugin in exactly the same way as in case of provider. If you do not want to use Stub Runner then you need to copy contracts stored in src/test/resources/contracts and generate WireMock JSON stubs using:

./gradlew generateClientStubs
[Note]Note

The stubsOutputDir option has to be set for stub generation to work.

When present, JSON stubs can be used in automated tests of consuming a service.

@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
 }
}

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

4.2 Maven Project

To learn how to set up the Maven project for Spring Cloud Contract Verifier, read the following sections:

4.2.1 Add maven plugin

Add the Spring Cloud Contract BOM in a fashion similar to this:

<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, add 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 Documentation.

4.2.2 Maven and Rest Assured 2.0

By default, Rest Assured 3.x is added to the classpath. However, you can use Rest Assured 2.x by adding it to the plugins classpath, as shown here:

<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.jayway.restassured</groupId>
           <artifactId>rest-assured</artifactId>
           <version>2.5.0</version>
           <scope>compile</scope>
        </dependency>
        <dependency>
           <groupId>com.jayway.restassured</groupId>
           <artifactId>spring-mock-mvc</artifactId>
           <version>2.5.0</version>
           <scope>compile</scope>
        </dependency>
    </dependencies>
</plugin>

<dependencies>
    <!-- all dependencies -->
    <!-- you can exclude rest-assured from spring-cloud-contract-verifier -->
    <dependency>
       <groupId>com.jayway.restassured</groupId>
       <artifactId>rest-assured</artifactId>
       <version>2.5.0</version>
       <scope>test</scope>
    </dependency>
    <dependency>
       <groupId>com.jayway.restassured</groupId>
       <artifactId>spring-mock-mvc</artifactId>
       <version>2.5.0</version>
       <scope>test</scope>
    </dependency>
</dependencies>

That way, the plugin automatically sees that Rest Assured 3.x is present on the classpath and modifies the imports accordingly.

4.2.3 Snapshot versions for Maven

For Snapshot and Milestone versions, you have to add the following section to your pom.xml, as shown here:

<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>

4.2.4 Add stubs

By default, Spring Cloud Contract Verifier is looking for stubs in the src/test/resources/contracts directory. The 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 to be used as test class name. If there is more than one level of nested directories, all except the last one is used as package name. For example, with following structure:

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

Spring Cloud Contract Verifier creates a test class named defaultBasePackage.MyService with two methods

  • shouldCreateUser()
  • shouldReturnUser()

4.2.5 Run plugin

The plugin goal generateTests is assigned to be invoked in the phase called generate-test-sources. If you want it to be part of your build process, you need not do anything. If you just want to generate tests, invoke the generateTests goal.

4.2.6 Configure plugin

To change the default configuration, just add a configuration section to the plugin definition or the execution definition, as shown here:

<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>

4.2.7 Configuration Options

  • testMode: Defines the mode for acceptance tests. By default, the mode is MockMvc, which is based on Spring’s MockMvc. It can also be changed to JaxRsClient or to Explicit for real HTTP calls.
  • basePackageForTests: Specifies the base package for all generated tests. If not set, the value is picked from baseClassForTests’s package and from `packageWithBaseClasses. If neither of these values are set, then the value is set to org.springframework.cloud.contract.verifier.tests.
  • ruleClassForTests: Specifies a rule that should be added to the generated test classes.
  • baseClassForTests: Creates a base class for all generated tests. By default, if you use Spock classes, the class is spock.lang.Specification.
  • contractsDirectory: Specifies a directory containing contracts written with the GroovyDSL. The default directory is /src/test/resources/contracts.
  • testFramework: Specifies the target test framework to be used. Currently, Spock and JUnit are supported with JUnit being the default framework
  • packageWithBaseClasses: Defines a package where all the base classes reside. This setting takes precedence over baseClassForTests. The convention is such that, if you have a contract under (for example) src/test/resources/contract/foo/bar/baz/ and set the value of the packageWithBaseClasses property to com.example.base, then Spring Cloud Contract Verifier assumes that there is a BarBazBase class under the com.example.base package. In other words, the system takes the last two parts of the package, if they exist, and forms a class with a Base suffix.
  • baseClassMappings: Specifies a list of base class mappings that provide contractPackageRegex, which is checked against the package where the contract is located, and baseClassFQN, which maps to the fully qualified name of the base class for the matched contract. For example, 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 extends com.example.base.BaseClass. This setting takes precedence over packageWithBaseClasses and baseClassForTests.

If you want to download your contract definitions from a Maven repository, you can use the following options:

  • contractDependency: The contract dependency that contains all the packaged contracts.
  • contractsPath: The path to the concrete contracts in the JAR with packaged contracts. Defaults to groupid/artifactid where gropuid is slash separated.
  • contractsWorkOffline: Dictates whether the dependencies should be downloaded or the local Maven artifacts should be reused.
  • contractsRepositoryUrl: URL to a repo with the artifacts that have contracts. If it is not provided, use the current Maven ones.
  • contractsRepositoryUsername: The user name to be used to connect to the repo with contracts.
  • contractsRepositoryPassword: The password to be used to connect to the repo with contracts.
  • contractsRepositoryProxyHost: The proxy host to be used to connect to the repo with contracts.
  • contractsRepositoryProxyPort: The proxy port to be used to connect to the repo with contracts.

We cache only non-snapshot, explicitly provided versions (for example + or 1.0.0.BUILD-SNAPSHOT won’t get cached). By default, this feature is turned on.

4.2.8 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 an 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())
  }
}

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

4.2.9 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

By Convention

The convention is such that if you have a contract under (for example) src/test/resources/contract/foo/bar/baz/ and set the value of the packageWithBaseClasses property to com.example.base, then Spring Cloud Contract Verifier assumes that there is a BarBazBase class under the com.example.base package. In other words, the system takes the last two parts of the package, if they exist, and forms a class with a Base suffix. This rule takes precedence over baseClassForTests. Here is an example of how it works in the contracts closure:

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

By 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 called baseClassMappings that consists baseClassMapping objects that takes a contractPackageRegex to baseClassFQN mapping. Consider 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>

Assume that you have contracts under these two locations: * src/test/resources/contract/com/ * src/test/resources/contract/foo/

By providing the baseClassForTests, we have a fallback in case mapping did not succeed. (You can also provide the packageWithBaseClasses as a fallback.) That way, the tests generated from src/test/resources/contract/com/ contracts extend the com.example.ComBase, whereas the rest of the tests extend com.example.FooBase.

4.2.10 Invoking generated tests

The Spring Cloud Contract Maven Plugin generates verification code in a directory called /generated-test-sources/contractVerifier and attaches this directory to testCompile goal.

For Groovy Spock code, use the following:

<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 compliant with defined contracts, you need to invoke mvn generateTest test.

4.2.11 Maven Plugin and STS

If you see the following exception while using STS:

STS Exception

When you click on the error marker you should see something 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, 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>

4.2.12 Spring Cloud Contract Verifier on the Consumer Side

You can also use the Spring Cloud Contract Verifier for the consumer side. To do so, 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 you would for a provider. You need to copy contracts stored in src/test/resources/contracts and generate WireMock JSON stubs using the mvn generateStubs command. By default, the generated WireMock mapping is stored in a directory named target/mappings. From these generated mappings, your project should create additional artifacts with a classifier of stubs for easy deployment to the maven repository.

Here is a 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, as shown here:

@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();
  }
}

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

4.3 Stubs and Transitive Dependencies

The Maven and Gradle plugin that add the tasks that create the stubs jar for you. One problem that arises is that, when reusing the stubs, you can mistakenly import all of that stub’s 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
  • Create a separate artifactid for the stubs
  • Exclude dependencies on the consumer side

Mark all application dependencies as optional

If, in the github-webhook application, you mark all of your 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 dependencies are optional, they will not get downloaded.

Create a separate artifactid for the stubs

If you create a separate artifactid, then you can set it up in whatever way you wish. For example, you might decide to have 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.

4.4 Scenarios

You can handle scenarios with Spring Cloud Contract Verifier. All you need to do is to stick to the proper naming convention while creating your contracts. The convention requires including an order number followed by an underscore, as shown in this example:

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

Such a tree causes Spring Cloud Contract Verifier to generate WireMock’s scenario with a name of scenario1 and the three following steps:

  1. login marked as Started pointing to…​
  2. showCart marked as Step1 pointing to…​
  3. logout marked as Step2 which will close the scenario.

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

Spring Cloud Contract Verifier also generates tests with a guaranteed order of execution.

5. Spring Cloud Contract Verifier Messaging

Spring Cloud Contract Verifier lets you verify applications that uses messaging as a means of communication. All of the integrations shown in this document work with Spring, but you can also create one of your own and use that.

5.1 Integrations

You can use one of the following four integration configurations:

  • Apache Camel
  • Spring Integration
  • Spring Cloud Stream
  • Spring AMQP

Since we use Spring Boot, if you have added one of these libraries to the classpath, all the messaging configuration is automatically set up.

[Important]Important

Remember to put @AutoConfigureMessageVerifier on the base class of your generated tests. Otherwise, messaging part of Spring Cloud Contract Verifier does not work.

[Important]Important

If you want to use Spring Cloud Stream, remember to add a dependency on org.springframework.cloud:spring-cloud-stream-test-support, as shown here:

Maven. 

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-stream-test-support</artifactId>
    <scope>test</scope>
</dependency>

Gradle. 

testCompile "org.springframework.cloud:spring-cloud-stream-test-support"

5.2 Manual Integration Testing

The main interface used by the tests is 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 a test, you can inject a ContractVerifierMessageExchange to send and receive messages that follow the contract. Then add @AutoConfigureMessageVerifier to your test. Here’s an example:

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

  @Autowired
  private MessageVerifier verifier;
  ...
}
[Note]Note

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

5.3 Publisher-Side Test Generation

Having the input or outputMessage sections in your DSL results in creation of tests on the publisher’s side. By default, JUnit tests are 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 message. The output message is triggered by a component inside the application (for example, scheduler).
  • Scenario 2: The input message triggers an output message.
  • Scenario 3: The input message is consumed and there is no output message.
[Important]Important

The destination passed to messageFrom or sentTo can have different meanings for different messaging implementations. For Stream and Integration it is first resolved as a destination of a channel. Then, if there is no such destination it is resolved as a channel name. For Camel, that’s a certain component (for example, jms).

5.3.1 Scenario 1: No Input Message

Here is an example for Camel. 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')
			messagingContentType(applicationJson())
		}
	}
}

The following JUnit test is created:

'''
 // when:
  bookReturnedTriggered();

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

'''

5.3.2 Scenario 2: Output Triggered by Input

Here is an example for Camel. 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 is 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")).isNotNull();
 assertThat(response.getHeader("BOOK-NAME").toString()).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')?.toString()  == 'foo'
and:
   DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.payload))
   assertThatJson(parsedJson).field("bookName").isEqualTo("foo")
"""

5.3.3 Scenario 3: No Output Message

Here is an example for Camel. 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 is 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()
'''

5.4 Consumer Stub Generation

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

For more information, see 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>Finchley.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
		}
	}
}

6. Spring Cloud Contract Stub Runner

One of the issues that you might encounter while using Spring Cloud Contract Verifier is passing the generated WireMock JSON stubs from the server side to the client side (or to various clients). The same takes place in terms of client-side generation for messaging.

Copying the JSON files and setting the client side for messaging manually is out of the question. That is why we introduced Spring Cloud Contract Stub Runner. It can automatically download and run the stubs for you.

6.1 Snapshot versions

Add the additional snapshot repository to your build.gradle file 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" }
	}

6.2 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]Tip

For both Maven and Gradle, the setup comes ready to work. However, 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 -->
<!-- we want the assembly plugin to generate the JAR -->
<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>
				<descriptors>
					${basedir}/src/assembly/stub.xml
				</descriptors>
			</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
		}
	}
}

6.3 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 (or pick those from the classpath), start WireMock servers for them and feed them with proper stub definitions. For messaging, special stub routes are defined.

6.3.1 Retrieving stubs

You can pick the following options of acquiring stubs

  • Aether based solution that downloads JARs with stubs from Artifactory / Nexus
  • Classpath scanning solution that searches classpath via pattern to retrieve stubs
  • Write your own implementation of the org.springframework.cloud.contract.stubrunner.StubDownloaderBuilder for full customization

The latter example is described in the Custom Stub Runner section.

Stub downloading

You can control the stub downloading via the stubsMode switch. It picks value from the StubRunnerProperties.StubsMode enum. You can use the following options

  • StubRunnerProperties.StubsMode.CLASSPATH (default value) - will pick stubs from the classpath
  • StubRunnerProperties.StubsMode.LOCAL - will pick stubs from a local storage (e.g. .m2)
  • StubRunnerProperties.StubsMode.REMOTE - will pick stubs from a remote location

Example:

@AutoConfigureStubRunner(repositoryRoot="http://foo.bar", ids = "com.example:beer-api-producer:+:stubs:8095", stubsMode = StubRunnerProperties.StubsMode.LOCAL)

Classpath scanning

If you set the stubsMode property to StubRunnerProperties.StubsMode.CLASSPATH (or set nothing since CLASSPATH is the default value) then classpath will get scanned. Let’s look at the following example:

@AutoConfigureStubRunner(ids = {
    "com.example:beer-api-producer:+:stubs:8095",
    "com.example.foo:bar:1.0.0:superstubs:8096"
})

If you’ve added the dependencies to your classpath

Maven. 

<dependency>
    <groupId>com.example</groupId>
    <artifactId>beer-api-producer-restdocs</artifactId>
    <classifier>stubs</classifier>
    <version>0.0.1-SNAPSHOT</version>
    <scope>test</scope>
    <exclusions>
        <exclusion>
            <groupId>*</groupId>
            <artifactId>*</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>com.example.foo</groupId>
    <artifactId>bar</artifactId>
    <classifier>superstubs</classifier>
    <version>1.0.0</version>
    <scope>test</scope>
    <exclusions>
        <exclusion>
            <groupId>*</groupId>
            <artifactId>*</artifactId>
        </exclusion>
    </exclusions>
</dependency>

Gradle. 

testCompile("com.example:beer-api-producer-restdocs:0.0.1-SNAPSHOT:stubs") {
    transitive = false
}
testCompile("com.example.foo:bar:1.0.0:superstubs") {
    transitive = false
}

Then the following locations on your classpath will get scanned. For com.example:beer-api-producer-restdocs

  • /META-INF/com.example/beer-api-producer-restdocs/*/.*
  • /contracts/com.example/beer-api-producer-restdocs/*/.*
  • /mappings/com.example/beer-api-producer-restdocs/*/.*

and com.example.foo:bar

  • /META-INF/com.example.foo/bar/*/.*
  • /contracts/com.example.foo/bar/*/.*
  • /mappings/com.example.foo/bar/*/.*
[Tip]Tip

As you can see you have to explicitly provide the group and artifact ids when packaging the producer stubs.

The producer would setup the contracts like this:

└── src
    └── test
        └── resources
            └── contracts
                └── com.example
                    └── beer-api-producer-restdocs
                        └── nested
                            └── contract3.groovy

To achieve proper stub packaging.

Or using the Maven assembly plugin or Gradle Jar task you have to create the following structure in your stubs jar.

└── META-INF
    └── com.example
        └── beer-api-producer-restdocs
            └── 2.0.0
                ├── contracts
                │   └── nested
                │       └── contract2.groovy
                └── mappings
                    └── mapping.json

By maintaining this structure classpath gets scanned and you can profit from the messaging / HTTP stubs without the need to download artifacts.

6.3.2 Running stubs

Limitations

[Important]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
--sm, --stubsMode               Stubs mode to be used. Acceptable values
                                  [CLASSPATH, LOCAL, REMOTE]
-u, --username                  Username to user when connecting to
                                  repository

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.

You can also use the mappingsOutputFolder property to dump the mappings to files. For annotation based approach it would look like this

@AutoConfigureStubRunner(ids="a.b.c:loanIssuance,a.b.c:fraudDetectionServer",
mappingsOutputFolder = "target/outputmappings/")

and for the JUnit approach like this:

@ClassRule @Shared StubRunnerRule rule = new StubRunnerRule()
			.repoRoot("http://some_url")
			.downloadStub("a.b.c", "loanIssuance")
			.downloadStub("a.b.c:fraudDetectionServer")
			.withMappingsOutputFolder("target/outputmappings")

Then if you check out the folder target/outputmappings you would see the following structure

.
├── fraudDetectionServer_13705
└── loanIssuance_12255

That means that there were two stubs registered. fraudDetectionServer was registered at port 13705 and loanIssuance at port 12255. If we take a look at one of the files we would see (for WireMock) mappings available for the given server:

[{
  "id" : "f9152eb9-bf77-4c38-8289-90be7d10d0d7",
  "request" : {
    "url" : "/name",
    "method" : "GET"
  },
  "response" : {
    "status" : 200,
    "body" : "fraudDetectionServer"
  },
  "uuid" : "f9152eb9-bf77-4c38-8289-90be7d10d0d7"
},
...
]

Messaging Stubs

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

6.4 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
  • can also send messages (remember to pass an implementation of MessageVerifier interface)

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:

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()
		.stubsMode(StubRunnerProperties.StubsMode.REMOTE)
		.repoRoot(StubRunnerRuleSpec.getResource("/m2repo/repository").toURI().toString())
		.downloadStub("org.springframework.cloud.contract.verifier.stubs", "loanIssuance")
		.downloadStub("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer")
		.withMappingsOutputFolder("target/outputmappingsforrule")


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'
}

def 'should output mappings to output folder'() {
	when:
		def url = rule.findStubUrl('fraudDetectionServer')
	then:
		new File("target/outputmappingsforrule", "fraudDetectionServer_${url.port}").exists()
}

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.

[Important]Important

To use the JUnit rule together with messaging you have to provide an implementation of the MessageVerifier interface to the rule builder (e.g. rule.messageVerifier(new MyMessageVerifier())). If you don’t do this then whenever you try to send a message an exception will be thrown.

6.4.1 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.

6.4.2 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.

6.4.3 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());

6.4.4 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",
		'foo=${stubrunner.runningstubs.fraudDetectionServer.port}'])
@AutoConfigureStubRunner(mappingsOutputFolder = "target/outputmappings/")
@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
	}

	def 'should dump all mappings to a file'() {
		when:
			def url = stubFinder.findStubUrl("fraudDetectionServer")
		then:
			new File("target/outputmappings/", "fraudDetectionServer_${url.port}").exists()
	}

	@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
  stubs-mode: remote

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"],
		stubsMode = StubRunnerProperties.StubsMode.REMOTE,
		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.

6.5 Stub Runner Spring Cloud

Stub Runner can integrate with Spring Cloud.

For real life examples you can check the

6.5.1 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

stubrunner:
  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");
    }

6.5.2 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]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.

6.6 Stub Runner Boot Application

Spring Cloud Contract 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 check out the Spring Cloud Pipelines project for more information.

6.6.1 How to use it?

Stub Runner Server

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.

Spring Cloud CLI

Starting from 1.4.0.RELEASE version of the Spring Cloud CLI project you can start Stub Runner Boot by executing spring cloud stubrunner.

In order to pass the configuration just create a stubrunner.yml file in the current working directory or a subdirectory called config or in ~/.spring-cloud. The file could look like this (example for running stubs installed locally)

stubrunner.yml. 

stubrunner:
  stubsMode: LOCAL
  ids:
    - com.example:beer-api-producer:+:9876

and then just call spring cloud stubrunner from your terminal window to start the Stub Runner server. It will be available at port 8750.

6.6.2 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)

6.6.3 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
			Integer.valueOf(response.body.asString()) > 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=")
	}

}

6.6.4 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.

6.7 Stubs Per Consumer

There are cases in which 2 consumers of the same endpoint want to have 2 different responses.

[Tip]Tip

This approach also allows you to immediately know which consumer is using which part of your API. You can remove part of a response that your API produces and you can see which of your autogenerated tests fails. If none fails then you can safely delete that part of the response cause nobody is using it.

Let’s look at the following example for contract defined for the producer called producer. There are 2 consumers: foo-consumer and bar-consumer.

Consumer foo-service

request {
   url '/foo'
   method GET()
}
response {
    status 200
    body(
       foo: "foo"
    }
}

Consumer bar-service

request {
   url '/foo'
   method GET()
}
response {
    status 200
    body(
       bar: "bar"
    }
}

You can’t produce for the same request 2 different responses. That’s why you can properly package the contracts and then profit from the stubsPerConsumer feature.

On the producer side the consumers can have a folder that contains contracts related only to them. By setting the stubrunner.stubs-per-consumer flag to true we no longer register all stubs but only those that correspond to the consumer application’s name. In other words we’ll scan the path of every stub and if it contains the subfolder with name of the consumer in the path only then will it get registered.

On the foo producer side the contracts would look like this

.
└── contracts
    ├── bar-consumer
    │   ├── bookReturnedForBar.groovy
    │   └── shouldCallBar.groovy
    └── foo-consumer
        ├── bookReturnedForFoo.groovy
        └── shouldCallFoo.groovy

Being the bar-consumer consumer you can either set the spring.application.name or the stubrunner.consumer-name to bar-consumer Or set the test as follows:

@ContextConfiguration(classes = Config, loader = SpringBootContextLoader)
@SpringBootTest(properties = ["spring.application.name=bar-consumer"])
@AutoConfigureStubRunner(ids = "org.springframework.cloud.contract.verifier.stubs:producerWithMultipleConsumers",
		repositoryRoot = "classpath:m2repo/repository/",
		stubsMode = StubRunnerProperties.StubsMode.REMOTE,
		stubsPerConsumer = true)
@DirtiesContext
class StubRunnerStubsPerConsumerSpec extends Specification {
...
}

Then only the stubs registered under a path that contains the bar-consumer in its name (i.e. those from the src/test/resources/contracts/bar-consumer/some/contracts/…​ folder) will be allowed to be referenced.

Or set the consumer name explicitly

@ContextConfiguration(classes = Config, loader = SpringBootContextLoader)
@SpringBootTest
@AutoConfigureStubRunner(ids = "org.springframework.cloud.contract.verifier.stubs:producerWithMultipleConsumers",
		repositoryRoot = "classpath:m2repo/repository/",
		consumerName = "foo-consumer",
		stubsMode = StubRunnerProperties.StubsMode.REMOTE,
		stubsPerConsumer = true)
@DirtiesContext
class StubRunnerStubsPerConsumerWithConsumerNameSpec extends Specification {
...
}

Then only the stubs registered under a path that contains the foo-consumer in its name (i.e. those from the src/test/resources/contracts/foo-consumer/some/contracts/…​ folder) will be allowed to be referenced.

You can check out issue 224 for more information about the reasons behind this change.

6.8 Common

This section briefly describes common properties, including:

6.8.1 Common Properties for JUnit and Spring

You can set repetitive properties by using system properties or Spring configuration properties. Here are their names with their default values:

Property nameDefault valueDescription

stubrunner.minPort

10000

Minimum value of a port for a started WireMock with stubs.

stubrunner.maxPort

15000

Maximum value of a port for a started WireMock with stubs.

stubrunner.repositoryRoot

 

Maven repo URL. If blank, then call the local maven repo.

stubrunner.classifier

stubs

Default classifier for the stub artifacts.

stubrunner.stubsMode

CLASSPATH

The way you want to fetch and register the 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.

stubrunner.stubsPerConsumer

false

Set to true if you want to use different stubs for each consumer instead of registering all stubs for every consumer.

stubrunner.consumerName

 

If you want to use a stub for each consumer and want to override the consumer name just change this value.

6.8.2 Stub Runner Stubs IDs

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

groupId:artifactId:version:classifier:port

Note that version, classifier and port are optional.

  • If you do not provide the port, a random one will be picked.
  • If you do not provide the classifier, the default is used. (Note that you can pass an empty classifier this way: groupId:artifactId:version:).
  • If you do not provide the version, then the + will be passed and the latest one is downloaded.

port means the port of the WireMock server.

[Important]Important

Starting with version 1.0.4, 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.

7. Stub Runner for Messaging

Stub Runner can run the published stubs in memory. It can integrate with the following frameworks:

  • Spring Integration
  • Spring Cloud Stream
  • Spring AMQP

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

[Important]Important

If you have multiple frameworks on the classpath Stub Runner will need to define which one should be used. Let’s assume that you have both AMQP, Spring Cloud Stream and Spring Integration on the classpath. Then you need to set stubrunner.stream.enabled=false and stubrunner.integration.enabled=false. That way the only remaining framework is Spring AMQP.

7.1 Stub triggering

To trigger a message, use the StubTrigger interface:

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 you only need one or the other in your tests.

StubTrigger gives you the following options to trigger a message:

7.1.1 Trigger by Label

stubFinder.trigger('return_book_1')

7.1.2 Trigger by Group and Artifact Ids

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

7.1.3 Trigger by Artifact Ids

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

7.1.4 Trigger All Messages

stubFinder.trigger()

7.2 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 automatically downloads the stubs and registers the required routes.

7.2.1 Adding the Runner to the Project

You can have both Spring Integration and Spring Cloud Contract Stub Runner on the classpath. Remember to annotate your test class with @AutoConfigureStubRunner.

7.2.2 Disabling the functionality

If you need to disable this functionality, set the stubrunner.integration.enabled=false property.

Assume that you have the following Maven repository with 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

Further assume the stubs contain the following structure:

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

Consider the following contracts (numbered 1):

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

Now consider 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"?>
<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>

These examples lend themselves to three scenarios:

Scenario 1 (no input message)

To trigger a message via the return_book_1 label, use the StubTigger interface, as follows:

stubFinder.trigger('return_book_1')

To listen to the output of the message sent to output:

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

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, you can send a message to the output destination:

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

To listen to the output of the message sent to output:

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

The received message passes 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, you can send a message to the input destination:

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

7.3 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 automatically downloads the stubs and registers the required routes.

[Warning]Warning

If Stub Runner’s integration with Stream the messageFrom or sentTo Strings are resolved first as a destination of a channel and no such destination exists, the destination is resolved as a channel name.

[Important]Important

If you want to use Spring Cloud Stream remember, to add a dependency on org.springframework.cloud:spring-cloud-stream-test-support.

Maven. 

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-stream-test-support</artifactId>
    <scope>test</scope>
</dependency>

Gradle. 

testCompile "org.springframework.cloud:spring-cloud-stream-test-support"

7.3.1 Adding the Runner to the Project

You can have both Spring Cloud Stream and Spring Cloud Contract Stub Runner on the classpath. Remember to annotate your test class with @AutoConfigureStubRunner.

7.3.2 Disabling the functionality

If you need to disable this functionality, set the stubrunner.stream.enabled=false property.

Assume that you 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

Further assume the stubs contain the following structure:

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

Consider the following contracts (numbered 1):

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

Now consider 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') }
	}
}

Now consider the following Spring configuration:

stubrunner.repositoryRoot: classpath:m2repo/repository/
stubrunner.ids: org.springframework.cloud.contract.verifier.stubs:streamService:0.0.1-SNAPSHOT:stubs
stubrunner.stubs-mode: remote
spring:
  cloud:
    stream:
      bindings:
        output:
          destination: returnBook
        input:
          destination: bookStorage

server:
  port: 0

debug: true

These examples lend themselves to three scenarios:

Scenario 1 (no input message)

To trigger a message via the return_book_1 label, use the StubTrigger interface as follows:

stubFinder.trigger('return_book_1')

To listen to the output of the message sent to a channel whose destination is returnBook:

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

The received message passes 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, you can send a message to the bookStorage destination:

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

To listen to the output of the message sent to returnBook:

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

The received message passes 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, you can send a message to the output destination:

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

7.4 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 automatically downloads the stubs and registers 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 named @SpyBean. As a result, it can use the mockito spy functionality to verify and inspect messages sent by the application.

On the message consumer side, the stub runner considers all @RabbitListener annotated endpoints and all SimpleMessageListenerContainer objects 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 looks for bindings on the application context that match this exchange. Then it collects the queues from the Spring exchanges and tries to find message listeners bound to these queues. The message is triggered for all matching message listeners.

7.4.1 Adding the Runner to the Project

You can 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 @AutoConfigureStubRunner.

[Important]Important

If you already have Stream and Integration on the classpath, you need to disable them explicitly by setting the stubrunner.stream.enabled=false and stubrunner.integration.enabled=false properties.

Assume that you 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

Further assume that the stubs contain the following structure:

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

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"
        ])
    }
}

Now consider 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
  stubs-mode: remote
  amqp:
    enabled: true
server:
  port: 0

Triggering the message

To trigger a message using the contract above, use the StubTrigger interface as follows:

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

The message has a destination of 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. As a result, the following listener definition is matched and 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 matches and is 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]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 Spring AMQP trying to connect to a running broker during our tests configure a mock ConnectionFactory.

To disable the mocked ConnectionFactory, set the following property: stubrunner.amqp.mockConnection=false

stubrunner:
  amqp:
    mockConnection: false

8. Contract DSL

[Important]Important

Remember that, inside the contract file, you have to provide the fully qualified name to the Contract class and make static imports, such as 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 do not be alarmed if you have not used Groovy before. Knowledge of the language is not really needed, as the Contract DSL uses only a tiny subset of it (only literals, method calls and closures). Also, the DSL is statically typed, to make it programmer-readable without any knowledge of the DSL itself.

[Tip]Tip

Spring Cloud Contract supports defining multiple contracts in a single file.

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

The following is a complete 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
	}
}
[Note]Note

The preceding example does not contain all the features of the DSL appear. The remainder of this section describes the other features.

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

8.1 Limitations

[Warning]Warning

Spring Cloud Contract Verifier does not properly support XML. Please use JSON or help us implement this feature.

[Warning]Warning

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

[Warning]Warning

Because JSON structure can have any form, it can be impossible to parse it properly when using the value(consumer(…​), producer(…​)) notation in GString. That is why you should use the Groovy Map notation.

8.2 Common Top-Level elements

The following sections describe the most common top-level elements:

8.2.1 Description

You can add a description to your contract. The description is arbitrary text. The following code shows an example:

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

8.2.2 Name

You can provide a name for your contract. Assume that you provided the following name: should register a user. If you do so, the name of the autogenerated test is validate_should_register_a_user. Also, the name of the stub in a WireMock stub is should_register_a_user.json.

[Important]Important

You must ensure that the name does not contain any characters that make the generated test not compile. Also, remember that, if you provide the same name for multiple contracts, your autogenerated tests fail to compile and your generated stubs override each other.

8.2.3 Ignoring Contracts

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

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

8.2.4 Passing Values from Files

Starting with version 1.2.0, you can pass values from files. Assume that you have the following resources in our project.

└── src
    └── test
        └── resources
            └── contracts
                ├── readFromFile.groovy
                ├── request.json
                └── response.json

Further assume that your contract is as follows:

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

Contract.make {
	request {
		method('PUT')
		headers {
			contentType(applicationJson())
		}
		body(file("request.json"))
		url("/1")
	}
	response {
		status 200
		body(file("response.json"))
		headers {
			contentType(textPlain())
		}
	}
}

Further assume that the JSON files is as follows:

request.json

{ "status" : "REQUEST" }

response.json

{ "status" : "RESPONSE" }

When test or stub generation takes place, the contents of the file is passed to the body of a request or a response. That works because of the file(…​) method. The argument of that method needs to be a file with location relative to the folder in which the contract lays.

8.2.5 HTTP Top-Level Elements

The 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
}

8.3 Request

The 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 an absolute rather than relative url, but using urlPath is the recommended way, as doing so 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 {
		//...
	}
}

request may contain additional request headers, as shown in the following example:

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 {
		//...
	}
}

request may contain a request body, as shown in the following example:

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 {
		//...
	}
}

request may contain multipart elements. To include multipart elements, call the multipart() method, as shown in the following example

org.springframework.cloud.contract.spec.Contract contractDsl = org.springframework.cloud.contract.spec.Contract.make {
	request {
		method "PUT"
		url "/multipart"
		headers {
			contentType('multipart/form-data;boundary=AaB03x')
		}
		multipart(
				// key (parameter name), value (parameter value) pair
				formParameter: $(c(regex('".+"')), p('"formParameterValue"')),
				someBooleanParameter: $(c(regex(anyBoolean())), p('true')),
				// a named parameter (e.g. with `file` name) that represents file with
				// `name` and `content`. You can also call `named("fileName", "fileContent")`
				file: named(
						// name of the file
						name: $(c(regex(nonEmpty())), p('filename.csv')),
						// content of the file
						content: $(c(regex(nonEmpty())), p('file content')))
		)
	}
	response {
		status 200
	}
}

In the preceding example, we define parameters in either of two ways:

  • Directly, by using the map notation, where the value can be a dynamic property (such as formParameter: $(consumer(…​), producer(…​))).
  • By using the named(…​) method that lets you set a named parameter. A named parameter can set a name and content. You can call it either via a method with two arguments, such as named("fileName", "fileContent"), or via a map notation, such as named(name: "fileName", content: "fileContent").

From this contract, the generated test is as follows:

// given:
 MockMvcRequestSpecification request = given()
   .header("Content-Type", "multipart/form-data;boundary=AaB03x")
   .param("formParameter", "\"formParameterValue\"")
   .param("someBooleanParameter", "true")
   .multiPart("file", "filename.csv", "file content".getBytes());

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

// then:
 assertThat(response.statusCode()).isEqualTo(200);

The WireMock stub is as follows:

			'''
{
  "request" : {
	"url" : "/multipart",
	"method" : "PUT",
	"headers" : {
	  "Content-Type" : {
		"matches" : "multipart/form-data;boundary=AaB03x.*"
	  }
	},
	"bodyPatterns" : [ {
		"matches" : ".*--(.*)\\r\\nContent-Disposition: form-data; name=\\"formParameter\\"\\r\\n(Content-Type: .*\\r\\n)?(Content-Length: \\\\d+\\r\\n)?\\r\\n\\".+\\"\\r\\n--\\\\1.*"
  		}, {
    			"matches" : ".*--(.*)\\r\\nContent-Disposition: form-data; name=\\"someBooleanParameter\\"\\r\\n(Content-Type: .*\\r\\n)?(Content-Length: \\\\d+\\r\\n)?\\r\\n(true|false)\\r\\n--\\\\1.*"
  		}, {
	  "matches" : ".*--(.*)\\r\\nContent-Disposition: form-data; name=\\"file\\"; filename=\\"[\\\\S\\\\s]+\\"\\r\\n(Content-Type: .*\\r\\n)?(Content-Length: \\\\d+\\r\\n)?\\r\\n[\\\\S\\\\s]+\\r\\n--\\\\1.*"
	} ]
  },
  "response" : {
	"status" : 200,
	"transformers" : [ "response-template", "foo-transformer" ]
  }
}
	'''

8.4 Response

The response must contain an HTTP status code and may contain other information. The following code shows an example:

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

8.5 Dynamic properties

The contract can contain some dynamic properties: timestamps, IDs, and so on. You do not want to force the consumers to stub their clocks to always return the same value of time so that it gets matched by the stub. You can provide the dynamic parts in your contracts in two ways: pass them directly in the body or set them in separate sections called testMatchers and stubMatchers.

8.5.1 Dynamic properties inside the body

You can set the properties inside the body either with the value method or, if you use the Groovy map notation, with $(). The following example shows how to set dynamic properties with the value method:

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

The following example shows how to set dynamic properties with $():

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

Both approaches work equally well. stub and client methods are aliases over the consumer method. Subsequent sections take a closer look at what you can do with those values.

8.5.2 Regular expressions

You can use regular expressions to write your requests in Contract DSL. Doing so 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 regular expressions when you need to use patterns and not exact values both for your test and your server side tests.

The following example shows how to use regular expressions to write a request:

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 with a regular expression. If you do so, then the contract engine automatically provides the generated string that matches the provided regular expression. The following code shows an 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 the preceding example, the opposite side of the communication has the respective data generated for request and response.

Spring Cloud Contract comes with a series of predefined regular expressions that you can use in your contracts, as shown in the following example:

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+|\\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._%+-][email protected][a-zA-Z0-9.-]+\\.[a-zA-Z]{2,6}')
protected static final Pattern URL = UrlHelper.URL
protected static final Pattern UUID = Pattern.compile('[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{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])')
protected static final Pattern NON_EMPTY = Pattern.compile(/[\S\s]+/)
protected static final Pattern NON_BLANK = Pattern.compile(/^\s*\S[\S\s]*/)
protected static final Pattern ISO8601_WITH_OFFSET = 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])(\.\d{3})?(Z|[+-][01]\d:[0-5]\d)/)

protected static Pattern anyOf(String... values){
	return Pattern.compile(values.collect({"^$it\$"}).join("|"))
}

Pattern onlyAlphaUnicode() {
	return ONLY_ALPHA_UNICODE
}

Pattern number() {
	return NUMBER
}

Pattern anyBoolean() {
	return TRUE_OR_FALSE
}

Pattern ipAddress() {
	return IP_ADDRESS
}

Pattern hostname() {
	return HOSTNAME_PATTERN
}

Pattern email() {
	return EMAIL
}

Pattern url() {
	return URL
}

Pattern uuid(){
	return UUID
}

Pattern isoDate() {
	return ANY_DATE
}

Pattern isoDateTime() {
	return ANY_DATE_TIME
}

Pattern isoTime() {
	return ANY_TIME
}

Pattern iso8601WithOffset() {
	return ISO8601_WITH_OFFSET
}

Pattern nonEmpty() {
	return NON_EMPTY
}

Pattern nonBlank() {
	return NON_BLANK
}

In your contract, you can use it as shown in the following example:

Contract dslWithOptionalsInString = Contract.make {
	priority 1
	request {
		method POST()
		url '/users/password'
		headers {
			contentType(applicationJson())
		}
		body(
				email: $(consumer(optional(regex(email()))), producer('[email protected]')),
				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('[email protected]'))}]"
		)
	}
}

8.5.3 Passing Optional Parameters

It is possible to provide optional parameters in your contract. However, you can provide optional parameters only for the following:

  • STUB side of the Request
  • TEST side of the Response

The following example shows how to provide optional parameters:

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('[email protected]')),
				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 create a regular expression that must be present 0 or more times.

If you use Spock for, the following test would be generated from the previous example:

"""
 given:
  def request = given()
    .header("Content-Type", "application/json")
    .body('''{"email":"[email protected]","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)?")
"""

The following stub would also be generated:

'''
{
  "request" : {
    "url" : "/users/password",
    "method" : "POST",
    "bodyPatterns" : [ {
      "matchesJsonPath" : "$[?(@.['email'] =~ /([a-zA-Z0-9._%+-][email protected][a-zA-Z0-9.-]+\\\\.[a-zA-Z]{2,6})?/)]"
    }, {
      "matchesJsonPath" : "$[?(@.['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
}
'''

8.5.4 Executing Custom Methods on the Server Side

You can define a method call that executes on the server side during the test. Such a method can be added to the class defined as "baseClassForTests" in the configuration. The following code shows an example of the contract portion of the test case:

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
	}
}

The following code shows the base class portion of the test case:

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]Important

You cannot use both a String and execute to perform concatenation. For example, calling header('Authorization', 'Bearer ' + execute('authToken()')) leads to improper results. Instead, call header('Authorization', execute('authToken()')) and ensure that the authToken() method returns everything you need.

The type of the object read from the JSON can be one of the following, depending on the JSON path:

  • String: If you point to a String value in the JSON.
  • JSONArray: If you point to a List in the JSON.
  • Map: If you point to a Map in the JSON.
  • Number: If you point to Integer, Double etc. in the JSON.
  • Boolean: If you point to a Boolean in the JSON.

In the request part of the contract, you can specify that the body should be taken from a method.

[Important]Important

You must provide both the consumer and the producer side. The execute part is applied for the whole body - not for parts of it.

The following example shows how to read an object from JSON:

Contract contractDsl = Contract.make {
	request {
		method 'GET'
		url '/something'
		body(
				$(c("foo"), p(execute("hashCode()")))
		)
	}
	response {
		status 200
	}
}

The preceding example results in calling the hashCode() method in the request body. It should resemble the following code:

// given:
 MockMvcRequestSpecification request = given()
   .body(hashCode());

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

// then:
 assertThat(response.statusCode()).isEqualTo(200);

8.5.5 Referencing the Request from the Response

The best situation is to provide fixed values, but sometimes you need to reference a request in your response. To do so, you can use the fromRequest() method, which lets you reference a bunch of elements from the HTTP request. You can use the following options:

  • fromRequest().url(): Returns the request URL and query parameters.
  • fromRequest().query(String key): Returns the first query parameter with a given name.
  • fromRequest().query(String key, int index): Returns the nth query parameter with a given name.
  • fromRequest().path(): Returns the full path.
  • fromRequest().path(int index): Returns the nth path element.
  • fromRequest().header(String key): Returns the first header with a given name.
  • fromRequest().header(String key, int index): Returns the nth header with a given name.
  • fromRequest().body(): Returns the full request body.
  • fromRequest().body(String jsonPath): Returns the element from the request that matches the JSON Path.

Consider the following contract:

Contract contractDsl = Contract.make {
	request {
		method 'GET'
		url('/api/v1/xxxx') {
			queryParameters {
				parameter("foo", "bar")
				parameter("foo", "bar2")
			}
		}
		headers {
			header(authorization(), "secret")
			header(authorization(), "secret2")
		}
		body(foo: "bar", baz: 5)
	}
	response {
		status 200
		headers {
			header(authorization(), "foo ${fromRequest().header(authorization())} bar")
		}
		body(
				url: fromRequest().url(),
				path: fromRequest().path(),
				pathIndex: fromRequest().path(1),
				param: fromRequest().query("foo"),
				paramIndex: fromRequest().query("foo", 1),
				authorization: fromRequest().header("Authorization"),
				authorization2: fromRequest().header("Authorization", 1),
				fullBody: fromRequest().body(),
				responseFoo: fromRequest().body('$.foo'),
				responseBaz: fromRequest().body('$.baz'),
				responseBaz2: "Bla bla ${fromRequest().body('$.foo')} bla bla"
		)
	}
}

Running a JUnit test generation leads to a test that resembles the following example:

// given:
 MockMvcRequestSpecification request = given()
   .header("Authorization", "secret")
   .header("Authorization", "secret2")
   .body("{\"foo\":\"bar\",\"baz\":5}");

// when:
 ResponseOptions response = given().spec(request)
   .queryParam("foo","bar")
   .queryParam("foo","bar2")
   .get("/api/v1/xxxx");

// then:
 assertThat(response.statusCode()).isEqualTo(200);
 assertThat(response.header("Authorization")).isEqualTo("foo secret bar");
// and:
 DocumentContext parsedJson = JsonPath.parse(response.getBody().asString());
 assertThatJson(parsedJson).field("['fullBody']").isEqualTo("{\"foo\":\"bar\",\"baz\":5}");
 assertThatJson(parsedJson).field("['authorization']").isEqualTo("secret");
 assertThatJson(parsedJson).field("['authorization2']").isEqualTo("secret2");
 assertThatJson(parsedJson).field("['path']").isEqualTo("/api/v1/xxxx");
 assertThatJson(parsedJson).field("['param']").isEqualTo("bar");
 assertThatJson(parsedJson).field("['paramIndex']").isEqualTo("bar2");
 assertThatJson(parsedJson).field("['pathIndex']").isEqualTo("v1");
 assertThatJson(parsedJson).field("['responseBaz']").isEqualTo(5);
 assertThatJson(parsedJson).field("['responseFoo']").isEqualTo("bar");
 assertThatJson(parsedJson).field("['url']").isEqualTo("/api/v1/xxxx?foo=bar&foo=bar2");
 assertThatJson(parsedJson).field("['responseBaz2']").isEqualTo("Bla bla bar bla bla");

As you can see, elements from the request have been properly referenced in the response.

The generated WireMock stub should resemble the following example:

{
  "request" : {
    "urlPath" : "/api/v1/xxxx",
    "method" : "POST",
    "headers" : {
      "Authorization" : {
        "equalTo" : "secret2"
      }
    },
    "queryParameters" : {
      "foo" : {
        "equalTo" : "bar2"
      }
    },
    "bodyPatterns" : [ {
      "matchesJsonPath" : "$[?(@.['baz'] == 5)]"
    }, {
      "matchesJsonPath" : "$[?(@.['foo'] == 'bar')]"
    } ]
  },
  "response" : {
    "status" : 200,
    "body" : "{\"authorization\":\"{{{request.headers.Authorization.[0]}}}\",\"path\":\"{{{request.path}}}\",\"responseBaz\":{{{jsonpath this '$.baz'}}} ,\"param\":\"{{{request.query.foo.[0]}}}\",\"pathIndex\":\"{{{request.path.[1]}}}\",\"responseBaz2\":\"Bla bla {{{jsonpath this '$.foo'}}} bla bla\",\"responseFoo\":\"{{{jsonpath this '$.foo'}}}\",\"authorization2\":\"{{{request.headers.Authorization.[1]}}}\",\"fullBody\":\"{{{escapejsonbody}}}\",\"url\":\"{{{request.url}}}\",\"paramIndex\":\"{{{request.query.foo.[1]}}}\"}",
    "headers" : {
      "Authorization" : "{{{request.headers.Authorization.[0]}}};foo"
    },
    "transformers" : [ "response-template" ]
  }
}

Sending a request such as the one presented in the request part of the contract results in sending the following response body:

{
  "url" : "/api/v1/xxxx?foo=bar&foo=bar2",
  "path" : "/api/v1/xxxx",
  "pathIndex" : "v1",
  "param" : "bar",
  "paramIndex" : "bar2",
  "authorization" : "secret",
  "authorization2" : "secret2",
  "fullBody" : "{\"foo\":\"bar\",\"baz\":5}",
  "responseFoo" : "bar",
  "responseBaz" : 5,
  "responseBaz2" : "Bla bla bar bla bla"
}
[Important]Important

This feature works only with WireMock having a version greater than or equal to 2.5.1. The Spring Cloud Contract Verifier uses WireMock’s response-template response transformer. It uses Handlebars to convert the Mustache {{{ }}} templates into proper values. Additionally, it registers two helper functions:

  • escapejsonbody: Escapes the request body in a format that can be embedded in a JSON.
  • jsonpath: For a given parameter, find an object in the request body.

8.5.6 Registering Your Own WireMock Extension

WireMock lets you register custom extensions. By default, Spring Cloud Contract registers the transformer, which lets you reference a request from a response. If you want to provide your own extensions, you can register an implementation of the org.springframework.cloud.contract.verifier.dsl.wiremock.WireMockExtensions interface. Since we use the spring.factories extension approach, you can create an entry in META-INF/spring.factories file similar to the following:

org.springframework.cloud.contract.verifier.dsl.wiremock.WireMockExtensions=\
org.springframework.cloud.contract.stubrunner.provider.wiremock.TestWireMockExtensions

The following is an example of a custom extension:

TestWireMockExtensions.groovy. 

package org.springframework.cloud.contract.verifier.dsl.wiremock

import com.github.tomakehurst.wiremock.extension.Extension

/**
 * Extension that registers the default transformer and the custom one
 */
class TestWireMockExtensions implements WireMockExtensions {
	@Override
	List<Extension> extensions() {
		return [
				new DefaultResponseTransformer(),
				new CustomExtension()
		]
	}
}

class CustomExtension implements Extension {

	@Override
	String getName() {
		return "foo-transformer"
	}
}

[Important]Important

Remember to override the applyGlobally() method and set it to false if you want the transformation to be applied only for a mapping that explicitly requires it.

8.5.7 Dynamic Properties in the Matchers Sections

If you work with Pact, the following discussion may seem familiar. Quite a few users are used to having a separation between the body and setting the dynamic parts of a contract.

You can use two separate sections:

  • stubMatchers, which lets you define the dynamic values that should end up in a stub. You can set it in the request or inputMessage part of your contract.
  • testMatchers, which is present in the response or outputMessage side of the contract.

Currently, Spring Cloud Contract Verifier supports only JSON Path-based matchers with the following matching possibilities:

  • For stubMatchers:

    • byEquality(): The value taken from the response via the provided JSON Path must be equal to the value provided in the contract.
    • byRegex(…​): The value taken from the response via the provided JSON Path must match the regex.
    • byDate(): The value taken from the response via the provided JSON Path must match the regex for an ISO Date value.
    • byTimestamp(): The value taken from the response via the provided JSON Path must match the regex for an ISO DateTime value.
    • byTime(): The value taken from the response via the provided JSON Path must match the regex for an ISO Time value.
  • For testMatchers:

    • byEquality(): The value taken from the response via the provided JSON Path must be equal to the provided value in the contract.
    • byRegex(…​): The value taken from the response via the provided JSON Path must match the regex.
    • byDate(): The value taken from the response via the provided JSON Path must match the regex for an ISO Date value.
    • byTimestamp(): The value taken from the response via the provided JSON Path must match the regex for an ISO DateTime value.
    • byTime(): The value taken from the response via the provided JSON Path must match the regex for an ISO Time value.
    • 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, in which you can set minOccurrence and maxOccurrence. That way, you can assert the size of the flattened collection. To check the size of an unflattened collection, use a custom method with the byCommand(…​) testMatcher.
    • byCommand(…​): The value taken from the response via the provided JSON Path is passed as an input to the custom method that you provide. For example, byCommand('foo($it)') results in calling a foo method to which the value matching the JSON Path gets passed. The type of the object read from the JSON can be one of the following, depending on the JSON path:

      • String: If you point to a String value.
      • JSONArray: If you point to a List.
      • Map: If you point to a Map.
      • Number: If you point to Integer, Double, or other kind of number.
      • Boolean: If you point to a Boolean.

Consider 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",
				key: [
						'complex.key' : 'foo'
				]
		])
		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('$.time', byTime())
			jsonPath("\$.['key'].['complex.key']", byEquality())
		}
		headers {
			contentType(applicationJson())
		}
	}
	response {
		status 200
		body([
				duck: 123,
				alpha: "abc",
				number: 123,
				aBoolean: true,
				date: "2017-01-01",
				dateTime: "2017-01-01T01:23:45",
				time: "01:02:34",
				valueWithoutAMatcher: "foo",
				valueWithTypeMatch: "string",
				valueWithMin: [
					1,2,3
				],
				valueWithMax: [
					1,2,3
				],
				valueWithMinMax: [
					1,2,3
				],
				valueWithMinEmpty: [],
				valueWithMaxEmpty: [],
				key: [
				        'complex.key' : 'foo'
				]
		])
		testMatchers {
			// asserts the jsonpath value against manual regex
			jsonPath('$.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)'))
			jsonPath("\$.['key'].['complex.key']", byEquality())
		}
		headers {
			contentType(applicationJson())
		}
	}
}

In the preceding example, you can see the dynamic portions of the contract in the matchers sections. For the request part, you can see that, for all fields but valueWithoutAMatcher, the values of the regular expressions that the stub should contain are explicitly set. For the valueWithoutAMatcher, the verification takes place in the same way as without the use of matchers. In that case, the test performs an equality check.

For the response side in the testMatchers section, we define the dynamic parts in a similar manner. The only difference is that the byType matchers are also present. The verifier engine checks four fields to verify whether the response from the test has a value for which the JSON path matches the given field, is of the same type as the one defined in the response body, and passes the following check (based on the method being called):

  • For $.valueWithTypeMatch, the engine checks whether the type is the same.
  • For $.valueWithMin, the engine check the type and asserts whether the size is greater than or equal to the minimum occurrence.
  • For $.valueWithMax, the engine checks the type and asserts whether the size is smaller than or equal to the maximum occurrence.
  • For $.valueWithMinMax, the engine checks the type and asserts whether the size is between the min and maximum occurrence.

The resulting test would resemble the following example (note that an and section separates the autogenerated assertions and the assertion from matchers):

// 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("$.valueWithMin")).isInstanceOf(java.util.List.class);
 assertThat((java.lang.Iterable) parsedJson.read("$.valueWithMin", java.util.Collection.class)).hasSizeGreaterThanOrEqualTo(1);
 assertThat((Object) parsedJson.read("$.valueWithMax")).isInstanceOf(java.util.List.class);
 assertThat((java.lang.Iterable) parsedJson.read("$.valueWithMax", java.util.Collection.class)).hasSizeLessThanOrEqualTo(3);
 assertThat((Object) parsedJson.read("$.valueWithMinMax")).isInstanceOf(java.util.List.class);
 assertThat((java.lang.Iterable) parsedJson.read("$.valueWithMinMax", java.util.Collection.class)).hasSizeBetween(1, 3);
 assertThat((Object) parsedJson.read("$.valueWithMinEmpty")).isInstanceOf(java.util.List.class);
 assertThat((java.lang.Iterable) parsedJson.read("$.valueWithMinEmpty", java.util.Collection.class)).hasSizeGreaterThanOrEqualTo(0);
 assertThat((Object) parsedJson.read("$.valueWithMaxEmpty")).isInstanceOf(java.util.List.class);
 assertThat((java.lang.Iterable) parsedJson.read("$.valueWithMaxEmpty", java.util.Collection.class)).hasSizeLessThanOrEqualTo(0);
 assertThatValueIsANumber(parsedJson.read("$.duck"));
[Important]Important

Notice that, for the byCommand method, the example calls the assertThatValueIsANumber. This method must be defined in the test base class or be statically imported to your tests. Notice that the byCommand call was converted to assertThatValueIsANumber(parsedJson.read("$.duck"));. That means that the engine took the method name and passed the proper JSON path as a parameter to it.

The resulting WireMock stub is in the following example:

				'''
{
  "request" : {
    "urlPath" : "/get",
    "method" : "POST",
    "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+|\\\\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" : "{\\"date\\":\\"2017-01-01\\",\\"dateTime\\":\\"2017-01-01T01:23:45\\",\\"number\\":123,\\"aBoolean\\":true,\\"duck\\":123,\\"alpha\\":\\"abc\\",\\"valueWithMin\\":[1,2,3],\\"time\\":\\"01:02:34\\",\\"valueWithTypeMatch\\":\\"string\\",\\"valueWithMax\\":[1,2,3],\\"valueWithMinMax\\":[1,2,3],\\"valueWithoutAMatcher\\":\\"foo\\"}",
    "headers" : {
      "Content-Type" : "application/json"
    }
  }
}
'''
[Important]Important

If you use a matcher, then the part of the request aned response that the matcher addresses with the JSON Path gets removed from the assertion. In the case of verifying a collection, you must create matchers for all the elements of the collection.

Consider the following example:

Contract.make {
    request {
        method 'GET'
        url("/foo")
    }
    response {
        status 200
        body(events: [[
                                 operation          : 'EXPORT',
                                 eventId            : '16f1ed75-0bcc-4f0d-a04d-3121798faf99',
                                 status             : 'OK'
                         ], [
                                 operation          : 'INPUT_PROCESSING',
                                 eventId            : '3bb4ac82-6652-462f-b6d1-75e424a0024a',
                                 status             : 'OK'
                         ]
                ]
        )
        testMatchers {
            jsonPath('$.events[0].operation', byRegex('.+'))
            jsonPath('$.events[0].eventId', byRegex('^([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})$'))
            jsonPath('$.events[0].status', byRegex('.+'))
        }
    }
}

The preceding code leads to creating the following test (the code block shows only the assertion section):

and:
	DocumentContext parsedJson = JsonPath.parse(response.body.asString())
	assertThatJson(parsedJson).array("['events']").contains("['eventId']").isEqualTo("16f1ed75-0bcc-4f0d-a04d-3121798faf99")
	assertThatJson(parsedJson).array("['events']").contains("['operation']").isEqualTo("EXPORT")
	assertThatJson(parsedJson).array("['events']").contains("['operation']").isEqualTo("INPUT_PROCESSING")
	assertThatJson(parsedJson).array("['events']").contains("['eventId']").isEqualTo("3bb4ac82-6652-462f-b6d1-75e424a0024a")
	assertThatJson(parsedJson).array("['events']").contains("['status']").isEqualTo("OK")
and:
	assertThat(parsedJson.read("\$.events[0].operation", String.class)).matches(".+")
	assertThat(parsedJson.read("\$.events[0].eventId", String.class)).matches("^([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})\$")
	assertThat(parsedJson.read("\$.events[0].status", String.class)).matches(".+")

As you can see, the assertion is malformed. Only the first element of the array got asserted. In order to fix this, you should apply the assertion to the whole $.events collection and assert it with the byCommand(…​) method.

8.6 JAX-RS Support

The Spring Cloud Contract Verifier supports the JAX-RS 2 Client API. The base class needs to define protected WebTarget webTarget and server initialization. The only option for testing JAX-RS API is to start a web server. Also, a request with a body needs to have a content type set. Otherwise, the default of application/octet-stream gets used.

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

testMode == 'JAXRSCLIENT'

The following example shows a generated test API:

'''
 // 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", "[email protected]")
    .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");
'''

8.7 Async Support

If you’re using asynchronous communication on the server side (your controllers are returning Callable, DeferredResult, and so on), then, inside your contract, you must provide a sync() method in the response section. The following code shows an example:

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

8.8 Working with Context Paths

Spring Cloud Contract supports context paths.

[Important]Important

The only change needed to fully support context paths is the switch on the PRODUCER side. Also, the autogenerated tests must use EXPLICIT mode. The consumer side remains untouched. In order for the generated test to pass, you must use 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 generate a test that DOES NOT use MockMvc. It means that you generate real requests and you need to setup your generated test’s base class to work on a real socket.

Consider the following contract:

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

The following example shows how to set up a base class and Rest Assured:

import io.restassured.RestAssured;
import org.junit.Before;
import org.springframework.boot.web.server.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;
	}
}

If you do it this way:

  • All of your requests in the autogenerated tests are sent to the real endpoint with your context path included (for example, /my-context-path/url).
  • Your contracts reflect that you have a context path. Your generated stubs also have that information (for example, in the stubs, you have to call /my-context-path/url).

8.9 Messaging Top-Level Elements

The DSL for messaging looks a little bit different than the one that focuses on HTTP. The following sections explain the differences:

8.9.1 Output Triggered by a Method

The output message can be triggered by calling a method (such as a Scheduler when a was started and a message was sent), as shown in the following example:

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 the previous example case, the output message is sent to output if a method called bookReturnedTriggered is executed. On the message publisher’s side, we generate a test that calls that method to trigger the message. On the consumer side, you can use the some_label to trigger the message.

8.9.2 Output Triggered by a Message

The output message can be triggered by receiving a message, as shown in the following example:

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 the preceding example, the output message is sent to output if a proper message is received on the input destination. On the message publisher’s side, the engine generates a test that sends the input message to the defined destination. On the consumer side, you can either send a message to the input destination or use a label (some_label in the example) to trigger the message.

8.9.3 Consumer/Producer

In HTTP, you have a notion of client/stub and `server/test notation. You can also use those paradigms in messaging. In addition, Spring Cloud Contract Verifier also provides the consumer and producer methods, as presented in the following example (note that 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'
		])
	}
}

8.9.4 Common

In the input {} or outputMessage {} section you can call assertThat with the name of a method (e.g. assertThatMessageIsOnTheQueue()) that you have defined in the base class or in a static import. Spring Cloud Pipelines will execute that method in the genertaed test.

8.10 Multiple Contracts in One File

You can define multiple contracts in one file. Such a contract might resemble the following example:

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

[
        Contract.make {
            name("should post a user")
            request {
                method 'POST'
                url('/users/1')
            }
            response {
                status 200
            }
        },
        Contract.make {
            request {
                method 'POST'
                url('/users/2')
            }
            response {
                status 200
            }
        }
]

In the preceding example, one contract has the name field and the other does not. This leads to generation of two tests that look more or less like this:

package org.springframework.cloud.contract.verifier.tests.com.hello;

import com.example.TestBase;
import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.JsonPath;
import com.jayway.restassured.module.mockmvc.specification.MockMvcRequestSpecification;
import com.jayway.restassured.response.ResponseOptions;
import org.junit.Test;

import static com.jayway.restassured.module.mockmvc.RestAssuredMockMvc.*;
import static com.toomuchcoding.jsonassert.JsonAssertion.assertThatJson;
import static org.assertj.core.api.Assertions.assertThat;

public class V1Test extends TestBase {

	@Test
	public void validate_should_post_a_user() throws Exception {
		// given:
			MockMvcRequestSpecification request = given();

		// when:
			ResponseOptions response = given().spec(request)
					.post("/users/1");

		// then:
			assertThat(response.statusCode()).isEqualTo(200);
	}

	@Test
	public void validate_withList_1() throws Exception {
		// given:
			MockMvcRequestSpecification request = given();

		// when:
			ResponseOptions response = given().spec(request)
					.post("/users/2");

		// then:
			assertThat(response.statusCode()).isEqualTo(200);
	}

}

Notice that, for the contract that has the name field, the generated test method is named validate_should_post_a_user. For the one that does not have the name, it is called validate_withList_1. It corresponds to the name of the file WithList.groovy and the index of the contract in the list.

The generated stubs is shown in the following example:

should post a user.json
1_WithList.json

As you can see, the first file got the name parameter from the contract. The second got the name of the contract file (WithList.groovy) prefixed with the index (in this case, the contract had an index of 1 in the list of contracts in the file).

[Tip]Tip

As you can see, it iss much better if you name your contracts because doing so makes your tests far more meaningful.

9. Customization

You can customize the Spring Cloud Contract Verifier by extending the DSL, as shown in the remainder of this section.

9.1 Extending the DSL

You can provide your own functions to the DSL. The key requirement for this feature is to maintain the static compatibility. Later in this document, you can see examples of:

  • Creating a JAR with reusable classes.
  • Referencing of these classes in the DSLs.

You can find the full example here.

9.1.1 Common JAR

The following examples show three classes that can be reused 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
 */
//tag::impl[]
public class PatternUtils {

	public static String tooYoung() {
		//remove::start[]
		return "[0-1][0-9]";
		//remove::end[return]
	}

	public static Pattern oldEnough() {
		//remove::start[]
		return Pattern.compile("[2-9][0-9]");
		//remove::end[return]
	}

	/**
	 * Makes little sense but it's just an example ;)
	 */
	public static Pattern ok() {
		//remove::start[]
		return Pattern.compile("OK");
		//remove::end[return]
	}
}
//end::impl[]

ConsumerUtils contains functions used by the consumer.

package com.example;

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

/**
 * 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
 */
//tag::impl[]
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 it's in the implementation that we decide what value we will pass to the consumer
	 * and which one to the producer.
	 *
	 * @author Marcin Grzejszczak
	 */
	public static ClientDslProperty oldEnough() {
		//remove::start[]
		// this example is not the best one and
		// theoretically you could just pass the regex instead of `ServerDslProperty` but
		// it's just to show some new tricks :)
		return new ClientDslProperty(PatternUtils.oldEnough(), 40);
		//remove::end[return]
	}

}
//end::impl[]

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
 */
//tag::impl[]
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 it's in the implementation that we decide what value we will pass to the consumer
	 * and which one to the producer.
	 */
	public static ServerDslProperty ok() {
		// this example is not the best one and
		// theoretically you could just pass the regex instead of `ServerDslProperty` but
		// it's just to show some new tricks :)
		return new ServerDslProperty( PatternUtils.ok(), "OK");
	}
}
//end::impl[]

9.1.2 Adding the Dependency to the 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.

9.1.3 Test the Dependency in the Project’s Dependencies

First, add the common jar dependency as a test dependency. Because your contracts files are available on the test resources path, the common jar classes automatically become visible in your Groovy files. The following examples show how to test the dependency:

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")

9.1.4 Test a Dependency in the Plugin’s Dependencies

Now, you must add the dependency for the plugin to reuse at runtime, as shown in the following example:

Maven. 

<plugin>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
	<version>${spring-cloud-contract.version}</version>
	<extensions>true</extensions>
	<configuration>
		<packageWithBaseClasses>com.example</packageWithBaseClasses>
		<baseClassMappings>
			<baseClassMapping>
				<contractPackageRegex>.*intoxication.*</contractPackageRegex>
				<baseClassFQN>com.example.intoxication.BeerIntoxicationBase</baseClassFQN>
			</baseClassMapping>
		</baseClassMappings>
	</configuration>
	<dependencies>
		<dependency>
			<groupId>com.example</groupId>
			<artifactId>beer-common</artifactId>
			<version>${project.version}</version>
			<scope>compile</scope>
		</dependency>
	</dependencies>
</plugin>

Gradle. 

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

9.1.5 Referencing classes in DSLs

You can now reference your classes in your DSL, as shown in the following example:

package contracts.beer.rest

import com.example.ConsumerUtils
import com.example.ProducerUtils
import org.springframework.cloud.contract.spec.Contract

Contract.make {
	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
```

""")
	request {
		method 'POST'
		url '/check'
		body(
				age: $(ConsumerUtils.oldEnough())
		)
		headers {
			contentType(applicationJson())
		}
	}
	response {
		status 200
		body("""
			{
				"status": "${value(ProducerUtils.ok())}"
			}
			""")
		headers {
			contentType(applicationJson())
		}
	}
}

10. Using the Pluggable Architecture

You may encounter cases where you have your contracts have been defined in other formats, such as YAML, RAML or PACT. In those cases, you still want to benefit from the automatic generation of tests and stubs. You can add your own implementation for generating both tests and stubs. Also, you can customize the way tests are generated (for example, you can generate tests for other languages) and the way stubs are generated (for example, you can generate stubs for other HTTP server implementations).

10.1 Custom Contract Converter

Assume that your contract is written in a YAML file as follows:

request:
  url: /foo
  method: PUT
  headers:
    foo: bar
  body:
    foo: bar
response:
  status: 200
  headers:
    foo2: bar
  body:
    foo2: bar

The ContractConverter interface lets you register your own implementation of a contract structure converter. The following code listing shows the ContractConverter interface:

package org.springframework.cloud.contract.spec

/**
 * Converter to be used to convert FROM {@link File} TO {@link Contract}
 * and from {@link Contract} to {@code T}
 *
 * @param <T> - type to which we want to convert the contract
 *
 * @author Marcin Grzejszczak
 * @since 1.1.0
 */
interface ContractConverter<T> {

	/**
	 * Should this file be accepted by the converter. Can use the file extension
	 * to check if the conversion is possible.
	 *
	 * @param file - file to be considered for conversion
	 * @return - {@code true} if the given implementation can convert the file
	 */
	boolean isAccepted(File file)

	/**
	 * Converts the given {@link File} to its {@link Contract} representation
	 *
	 * @param file - file to convert
	 * @return - {@link Contract} representation of the file
	 */
	Collection<Contract> convertFrom(File file)

	/**
	 * Converts the given {@link Contract} to a {@link T} representation
	 *
	 * @param contract - the parsed contract
	 * @return - {@link T} the type to which we do the conversion
	 */
	T convertTo(Collection<Contract> contract)
}

Your implementation must define the condition on which it should start the conversion. Also, you must define how to perform that conversion in both directions.

[Important]Important

Once you create your implementation, you must create a /META-INF/spring.factories file in which you provide the fully qualified name of your implementation.

The following example shows a typical spring.factories file:

# Converters
org.springframework.cloud.contract.spec.ContractConverter=\
org.springframework.cloud.contract.verifier.converter.YamlContractConverter

# tag::extension[]
org.springframework.cloud.contract.verifier.dsl.wiremock.WireMockExtensions=\
org.springframework.cloud.contract.verifier.dsl.wiremock.TestWireMockExtensions
# end::extension[]

The following example shows a typical YAML implementation that matches the preceding example:

package org.springframework.cloud.contract.verifier.converter

import java.nio.file.Files

import groovy.transform.CompileStatic
import org.springframework.cloud.contract.spec.Contract
import org.springframework.cloud.contract.spec.ContractConverter
import org.springframework.cloud.contract.spec.internal.Headers
import org.yaml.snakeyaml.Yaml

/**
 * Simple converter from and to a {@link YamlContract} to a collection of {@link Contract}
 */
@CompileStatic
class YamlContractConverter implements ContractConverter<List<YamlContract>> {

	@Override
	public boolean isAccepted(File file) {
		String name = file.getName()
		return name.endsWith(".yml") || name.endsWith(".yaml")
	}

	@Override
	public Collection<Contract> convertFrom(File file) {
		try {
			YamlContract yamlContract = new Yaml().loadAs(
					Files.newInputStream(file.toPath()), YamlContract.class)
			return [Contract.make {
				request {
					method(yamlContract?.request?.method)
					url(yamlContract?.request?.url)
					headers {
						yamlContract?.request?.headers?.each { String key, Object value ->
							header(key, value)
						}
					}
					body(yamlContract?.request?.body)
				}
				response {
					status(yamlContract?.response?.status)
					headers {
						yamlContract?.response?.headers?.each { String key, Object value ->
							header(key, value)
						}
					}
					body(yamlContract?.response?.body)
				}
			}]
		}
		catch (FileNotFoundException e) {
			throw new IllegalStateException(e)
		}
	}

	@Override
	public List<YamlContract> convertTo(Collection<Contract> contracts) {
		return contracts.collect { Contract contract ->
			YamlContract yamlContract = new YamlContract()
			yamlContract.request.with {
				method = contract?.request?.method?.clientValue
				url = contract?.request?.url?.clientValue
				headers = (contract?.request?.headers as Headers)?.asStubSideMap()
				body = contract?.request?.body?.clientValue as Map
			}
			yamlContract.response.with {
				status = contract?.response?.status?.clientValue as Integer
				headers = (contract?.response?.headers as Headers)?.asStubSideMap()
				body = contract?.response?.body?.clientValue as Map
			}
			return yamlContract
		}
	}
}

10.1.1 Pact Converter

Spring Cloud Contract includes support for Pact representation of contracts. Instead of using the Groovy DSL, you can use Pact files. In this section, we present how to add Pact support for your project.

10.1.2 Pact Contract

Consider following example of a Pact contract, which is a file under the src/test/resources/contracts folder.

{
  "provider": {
    "name": "Provider"
  },
  "consumer": {
    "name": "Consumer"
  },
  "interactions": [
    {
      "description": "",
      "request": {
        "method": "PUT",
        "path": "/fraudcheck",
        "headers": {
          "Content-Type": "application/vnd.fraud.v1+json"
        },
        "body": {
          "clientId": "1234567890",
          "loanAmount": 99999
        },
        "matchingRules": {
          "$.body.clientId": {
            "match": "regex",
            "regex": "[0-9]{10}"
          }
        }
      },
      "response": {
        "status": 200,
        "headers": {
          "Content-Type": "application/vnd.fraud.v1+json;charset=UTF-8"
        },
        "body": {
          "fraudCheckStatus": "FRAUD",
          "rejectionReason": "Amount too high"
        },
        "matchingRules": {
          "$.body.fraudCheckStatus": {
            "match": "regex",
            "regex": "FRAUD"
          }
        }
      }
    }
  ],
  "metadata": {
    "pact-specification": {
      "version": "2.0.0"
    },
    "pact-jvm": {
      "version": "2.4.18"
    }
  }
}

The remainder of this section about using Pact refers to the preceding file.

10.1.3 Pact for Producers

On the producer side, you mustadd two additional dependencies to your plugin configuration. One is the Spring Cloud Contract Pact support, and the other represents the current Pact version that you use.

Maven. 

<plugin>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-contract-maven-plugin</artifactId>
	<version>${spring-cloud-contract.version}</version>
	<extensions>true</extensions>
	<configuration>
		<packageWithBaseClasses>com.example.fraud</packageWithBaseClasses>
	</configuration>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-contract-spec-pact</artifactId>
			<version>${spring-cloud-contract.version}</version>
		</dependency>
		<dependency>
			<groupId>au.com.dius</groupId>
			<artifactId>pact-jvm-model</artifactId>
			<version>2.4.18</version>
		</dependency>
	</dependencies>
</plugin>

Gradle. 

classpath "org.springframework.cloud:spring-cloud-contract-spec-pact:${findProperty('verifierVersion') ?: verifierVersion}"
classpath 'au.com.dius:pact-jvm-model:2.4.18'

When you execute the build of your application, a test will be generated. The generated test might be as follows:

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

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

	// then:
		assertThat(response.statusCode()).isEqualTo(200);
		assertThat(response.header("Content-Type")).isEqualTo("application/vnd.fraud.v1+json;charset=UTF-8");
	// and:
		DocumentContext parsedJson = JsonPath.parse(response.getBody().asString());
		assertThatJson(parsedJson).field("rejectionReason").isEqualTo("Amount too high");
	// and:
		assertThat(parsedJson.read("$.fraudCheckStatus", String.class)).matches("FRAUD");
}

The corresponding generated stub might be as follows:

{
  "uuid" : "996ae5ae-6834-4db6-8fac-358ca187ab62",
  "request" : {
    "url" : "/fraudcheck",
    "method" : "PUT",
    "headers" : {
      "Content-Type" : {
        "equalTo" : "application/vnd.fraud.v1+json"
      }
    },
    "bodyPatterns" : [ {
      "matchesJsonPath" : "$[?(@.loanAmount == 99999)]"
    }, {
      "matchesJsonPath" : "$[?(@.clientId =~ /([0-9]{10})/)]"
    } ]
  },
  "response" : {
    "status" : 200,
    "body" : "{\"fraudCheckStatus\":\"FRAUD\",\"rejectionReason\":\"Amount too high\"}",
    "headers" : {
      "Content-Type" : "application/vnd.fraud.v1+json;charset=UTF-8"
    }
  }
}

10.1.4 Pact for Consumers

On the producer side, you must add two additional dependencies to your project dependencies. One is the Spring Cloud Contract Pact support, and the other represents the current Pact version that you use.

Maven. 

<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-contract-spec-pact</artifactId>
	<scope>test</scope>
</dependency>
<dependency>
	<groupId>au.com.dius</groupId>
	<artifactId>pact-jvm-model</artifactId>
	<version>2.4.18</version>
	<scope>test</scope>
</dependency>

Gradle. 

testCompile "org.springframework.cloud:spring-cloud-contract-spec-pact"
testCompile 'au.com.dius:pact-jvm-model:2.4.18'

10.2 Using the Custom Test Generator

If you want to generate tests for languages other than Java or you are not happy with the way the verifier builds Java tests, you can register your own implementation.

The SingleTestGenerator interface lets you register your own implementation. The following code listing shows the SingleTestGenerator interface:

package org.springframework.cloud.contract.verifier.builder

import org.springframework.cloud.contract.verifier.config.ContractVerifierConfigProperties
import org.springframework.cloud.contract.verifier.file.ContractMetadata
/**
 * Builds a single test.
 *
 * @since 1.1.0
 */
interface SingleTestGenerator {

	/**
	 * Creates contents of a single test class in which all test scenarios from
	 * the contract metadata should be placed.
	 *
	 * @param properties - properties passed to the plugin
	 * @param listOfFiles - list of parsed contracts with additional metadata
	 * @param className - the name of the generated test class
	 * @param classPackage - the name of the package in which the test class should be stored
	 * @param includedDirectoryRelativePath - relative path to the included directory
	 * @return contents of a single test class
	 */
	String buildClass(ContractVerifierConfigProperties properties, Collection<ContractMetadata> listOfFiles,
					  String className, String classPackage, String includedDirectoryRelativePath)

	/**
	 * Extension that should be appended to the generated test class. E.g. {@code .java} or {@code .php}
	 *
	 * @param properties - properties passed to the plugin
	 */
	String fileExtension(ContractVerifierConfigProperties properties)
}

Again, you must provide a spring.factories file, such as the one shown in the following example:

org.springframework.cloud.contract.verifier.builder.SingleTestGenerator=/
com.example.MyGenerator

10.3 Using the Custom Stub Generator

If you want to generate stubs for stub servers other than WireMock, you can plug in your own implementation of the StubGenerator interface. The following code listing shows the StubGenerator interface:

package org.springframework.cloud.contract.verifier.converter

import groovy.transform.CompileStatic
import org.springframework.cloud.contract.spec.Contract
import org.springframework.cloud.contract.verifier.file.ContractMetadata

/**
 * Converts contracts into their stub representation.
 *
 * @since 1.1.0
 */
@CompileStatic
interface StubGenerator {

	/**
	 * Returns {@code true} if the converter can handle the file to convert it into a stub.
	 */
	boolean canHandleFileName(String fileName)

	/**
	 * Returns the collection of converted contracts into stubs. One contract can
	 * result in multiple stubs.
	 */
	Map<Contract, String> convertContents(String rootName, ContractMetadata content)

	/**
	 * Returns the name of the converted stub file. If you have multiple contracts
	 * in a single file then a prefix will be added to the generated file. If you
	 * provide the {@link Contract#name} field then that field will override the
	 * generated file name.
	 *
	 * Example: name of file with 2 contracts is {@code foo.groovy}, it will be
	 * converted by the implementation to {@code foo.json}. The recursive file
	 * converter will create two files {@code 0_foo.json} and {@code 1_foo.json}
	 */
	String generateOutputFileNameForInput(String inputFileName)
}

Again, you must provide a spring.factories file, such as the one shown in the following example:

# Stub converters
org.springframework.cloud.contract.verifier.converter.StubGenerator=\
org.springframework.cloud.contract.verifier.wiremock.DslToWireMockClientConverter

The default implementation is the WireMock stub generation.

[Tip]Tip

You can provide multiple stub generator implementations. For example, from a single DSL, you can produce both WireMock stubs and Pact files.

10.4 Using the Custom Stub Runner

If you decide to use a custom stub generation, you also need a custom way of running stubs with your different stub provider.

Assume that you use Moco to build your stubs and that you have written a stub generator and placed your stubs in a JAR file.

In order for Stub Runner to know how to run your stubs, you have to define a custom HTTP Stub server implementation, which might resemble the following example:

package org.springframework.cloud.contract.stubrunner.provider.moco

import com.github.dreamhead.moco.bootstrap.arg.HttpArgs
import com.github.dreamhead.moco.runner.JsonRunner
import com.github.dreamhead.moco.runner.RunnerSetting
import groovy.util.logging.Slf4j
import org.springframework.cloud.contract.stubrunner.HttpServerStub
import org.springframework.util.SocketUtils

@Slf4j
class MocoHttpServerStub implements HttpServerStub {

	private boolean started
	private JsonRunner runner
	private int port

	@Override
	int port() {
		if (!isRunning()) {
			return -1
		}
		return port
	}

	@Override
	boolean isRunning() {
		return started
	}

	@Override
	HttpServerStub start() {
		return start(SocketUtils.findAvailableTcpPort())
	}

	@Override
	HttpServerStub start(int port) {
		this.port = port
		return this
	}

	@Override
	HttpServerStub stop() {
		if (!isRunning()) {
			return this
		}
		this.runner.stop()
		return this
	}

	@Override
	HttpServerStub registerMappings(Collection<File> stubFiles) {
		List<RunnerSetting> settings = stubFiles.findAll { it.name.endsWith("json") }
				.collect {
			log.info("Trying to parse [{}]", it.name)
			try {
				return RunnerSetting.aRunnerSetting().withStream(it.newInputStream()).build()
			} catch (Exception e) {
				log.warn("Exception occurred while trying to parse file [{}]", it.name, e)
				return null
			}
		}.findAll { it }
		this.runner = JsonRunner.newJsonRunnerWithSetting(settings,
				HttpArgs.httpArgs().withPort(this.port).build())
		this.runner.run()
		this.started = true
		return this
	}

	@Override
	String registeredMappings() {
		return ""
	}

	@Override
	boolean isAccepted(File file) {
		return file.name.endsWith(".json")
	}
}

Then, you can register it in your spring.factories file, as shown in the following example:

org.springframework.cloud.contract.stubrunner.HttpServerStub=\
org.springframework.cloud.contract.stubrunner.provider.moco.MocoHttpServerStub

Now you can run stubs with Moco.

[Important]Important

If you do not provide any implementation, then the default (WireMock) implementation is used. If you provide more than one, the first one on the list is used.

10.5 Using the Custom Stub Downloader

You can customize the way your stubs are downloaded by creating an implementation of the StubDownloaderBuilder interface, as shown in the following example:

package com.example;

class CustomStubDownloaderBuilder implements StubDownloaderBuilder {

	@Override
	public StubDownloader build(final StubRunnerOptions stubRunnerOptions) {
		return new StubDownloader() {
			@Override
			public Map.Entry<StubConfiguration, File> downloadAndUnpackStubJar(
					StubConfiguration config) {
				File unpackedStubs = retrieveStubs();
				return new AbstractMap.SimpleEntry<>(
						new StubConfiguration(config.getGroupId(), config.getArtifactId(), version,
								config.getClassifier()), unpackedStubs);
			}

			File retrieveStubs() {
			    // here goes your custom logic to provide a folder where all the stubs reside
			}
}

Then you can register it in your spring.factories file, as shown in the following example:

# Example of a custom Stub Downloader Provider
org.springframework.cloud.contract.stubrunner.StubDownloaderBuilder=\
com.example.CustomStubDownloaderBuilder

Now you can pick a folder with the source of your stubs.

[Important]Important

If you do not provide any implementation, then the default is used (scan classpath). If you provide the stubsMode = StubRunnerProperties.StubsMode.LOCAL or , stubsMode = StubRunnerProperties.StubsMode.REMOTE then the Aether implementation will be used If you provide more than one, then the first one on the list is used.

11. Spring Cloud Contract WireMock

The Spring Cloud Contract WireMock modules let you use WireMock in a Spring Boot application. Check out the samples for more details.

If you have a Spring Boot application that uses Tomcat as an embedded server (which is the default with spring-boot-starter-web), you can 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 behavior using a Java API or via static JSON declarations as part of your test. The following code shows an 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 (for example), @AutoConfigureWireMock(port=9999). For a random port, use a value of 0. The stub server port can be bound in the test application context with the "wiremock.server.port" property. 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, the same as for Spring integration tests.

11.1 Registering Stubs Automatically

If you use @AutoConfigureWireMock, it registers 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 an Ant-style resource pattern or a directory. In the case of a directory, */.json is appended. The following code shows an 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]Note

Actually, WireMock always loads mappings from src/test/resources/mappings as well as the custom locations in the stubs attribute. To change this behavior, you can also specify a files root as described in the next section of this document.

11.2 Using Files to Specify the Stub Bodies

WireMock can read response bodies from files on the classpath or the file system. In that case, you can 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 (by default, src/test/resources/__files). To customize this location you can set the files attribute in the @AutoConfigureWireMock annotation to the location of the parent directory (in other words, __files is a subdirectory). You can use Spring resource notation to refer to file:…​ or classpath:…​ locations. Generic URLs are not supported. A list of values can be given, in which case WireMock resolves the first file that exists when it needs to find a response body.

[Note]Note

When you configure the files root, it also affects the automatic loading of stubs, because 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.

11.3 Alternative: Using JUnit Rules

For a more conventional WireMock experience, you can use JUnit @Rules to start and stop the server. To do so, use the WireMockSpring convenience class to obtain an Options instance, as shown in the following example:

@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 @ClassRule means that the server shuts down after all the methods in this class have been run.

11.4 Relaxed SSL Validation for Rest Template

WireMock lets you stub a "secure" server with an "https" URL protocol. If your application wants to contact that stub server in an integration test, it will find that the SSL certificates are not valid (the usual problem with self-installed certificates). The best option is often to re-configure the client to use "http". If that’s not an option, you can ask Spring to configure an HTTP client that ignores SSL validation errors (do so only for tests, of course).

To make this work with minimum fuss, you need to be using the Spring Boot RestTemplateBuilder in your app, as shown in the following example:

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
	return builder.build();
}

You need RestTemplateBuilder because the builder is passed through callbacks to initialize it, so the SSL validation can be set up in the client at that point. This happens automatically in your test if you are using the @AutoConfigureWireMock annotation or the stub runner. If you use the JUnit @Rule approach, you need to add the @AutoConfigureHttpClient annotation as well, as shown in the following example:

@RunWith(SpringRunner.class)
@SpringBootTest("app.baseUrl=https://localhost:6443")
@AutoConfigureHttpClient
public class WiremockHttpsServerApplicationTests {

	@ClassRule
	public static WireMockClassRule wiremock = new WireMockClassRule(
			WireMockSpring.options().httpsPort(6443));
...
}

If you are using spring-boot-starter-test, you have the Apache HTTP client on the classpath and it is selected by the RestTemplateBuilder and configured to ignore SSL errors. If you use the default java.net client, you do not need the annotation (but it won’t do any harm). There is no support currently for other clients, but it may be added in future releases.

11.5 WireMock and Spring MVC Mocks

Spring Cloud Contract provides a convenience class that can load JSON WireMock stubs into a Spring MockRestServiceServer. The following code shows 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 value is prepended to all mock calls, and the stubs() method takes a stub path resource pattern as an argument. In the preceding example, the stub defined at /stubs/resource.json is loaded into the mock server. If the RestTemplate is asked to visit http://example.org/, it gets the responses as being declared at that URL. More than one stub pattern can be specified, and each one can be a directory (for a recursive list of all ".json"), a fixed filename (as 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, the Spring Cloud Contract Verifier supports 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).

11.6 Customization of WireMock configuration

You can register a bean of org.springframework.cloud.contract.wiremock.WireMockConfigurationCustomizer type in order to customize the WireMock configuration (e.g. add custom transformers). Example:

		@Bean WireMockConfigurationCustomizer optionsCustomizer() {
			return new WireMockConfigurationCustomizer() {
				@Override public void customize(WireMockConfiguration options) {
// perform your customization here
				}
			};
		}

11.7 Generating Stubs using REST Docs

Spring REST Docs can be used to generate documentation (for example in Asciidoctor format) for an HTTP API with Spring MockMvc or Rest Assured. At the same time that you generate documentation for your API, you can also generate WireMock stubs by using Spring Cloud Contract WireMock. To do so, write your normal REST Docs test cases and use @AutoConfigureRestDocs to have stubs be automatically generated in the REST Docs output directory. The following code shows an 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"));
	}
}

This test generates a WireMock stub at "target/snippets/stubs/resource.json". It matches all GET requests to the "/resource" path.

Without any additional configuration, this tests creates 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. Doing so has two effects:

  • Creating a stub that matches only in the way you specify.
  • Asserting that the request in the test case also matches the same conditions.

The main entry point for this feature is WireMockRestDocs.verify(), which can be used as a substitute for the document() convenience method, as shown in the following 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"));
	}
}

This contract specifies that any valid POST with an "id" field receives the response defined in this test. You can chain together calls to .jsonPath() to add additional matchers. If JSON Path is unfamiliar, The JayWay documentation can help you get up to speed.

Instead of the jsonPath and contentType convenience methods, you can also use the WireMock APIs to verify that the request matches the created stub, as shown in the following 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. These features can be used to create stubs with a wider range of parameters. The above example generates a stub resembling the following example:

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]Note

You can use either the wiremock() method or the jsonPath() and contentType() methods to create request matchers, but you can’t use both approaches.

On the consumer side, you can make the resource.json generated earlier in this section available on the classpath (by publishing stubs as JARs, for example). After that, you can create a stub using WireMock in a number of different ways, including by using @AutoConfigureWireMock(stubs="classpath:resource.json"), as described earlier in this document.

11.8 Generating Contracts by Using REST Docs

You can also generate Spring Cloud Contract DSL files and documentation with Spring REST Docs. If you do so in combination with Spring Cloud WireMock, you get both the contracts and the stubs.

Why would you want to use this feature? Some people in the community asked questions about a situation in which they would like to move to DSL-based contract definition, but they already have a lot of Spring MVC tests. Using this feature lets you generate the contract files that you can later modify and move to folders (defined in your configuration) so that the plugin finds them.

[Tip]Tip

You might wonder why this functionality is in the WireMock module. The functionality is there because it makes sense to generate both the contracts and the stubs.

Consider the following test:

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

The preceding test creates the stub presented in the previous section, generating both the contract and a documentation file.

The contract is called index.groovy and might look like the following example:

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

Contract.make {
    request {
        method 'POST'
        url '/foo'
        body('''
            {"foo": 23 }
        ''')
        headers {
            header('''Accept''', '''application/json''')
            header('''Content-Type''', '''application/json''')
        }
    }
    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 (formatted in Asciidoc in this case) contains a formatted contract. The location of this file would be index/dsl-contract.adoc.

12. Migrations

This section covers migrating from one version of Spring Cloud Contract Verifier to the next version. It covers the following versions upgrade paths:

12.1 1.0.x → 1.1.x

This section covers upgrading from version 1.0 to version 1.1.

12.1.1 New structure of generated stubs

In 1.1.x we have introduced a change to the structure of generated stubs. If you have been using the @AutoConfigureWireMock notation to use the stubs from the classpath, it no longer works. The following example shows how the @AutoConfigureWireMock notation used to work:

@AutoConfigureWireMock(stubs = "classpath:/customer-stubs/mappings", port = 8084)

You must either change the location of the stubs to: classpath:…​/META-INF/groupId/artifactId/version/mappings or use the new classpath-based @AutoConfigureStubRunner, as shown in the following example:

@AutoConfigureWireMock(stubs = "classpath:customer-stubs/META-INF/travel.components/customer-contract/1.0.2-SNAPSHOT/mappings/", port = 8084)

If you do not want to use @AutoConfigureStubRunner and you want to remain with the old structure, set your plugin tasks accordingly. The following example would work for the structure presented in the previous snippet.

Maven. 

<!-- start of pom.xml -->

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

<!-- ... -->

<!-- You need to set up the assembly plugin -->
<build>
    <plugins>
        <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>
    </plugins>
</build>
<!-- end of pom.xml -->

<!-- start of 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>${project.build.directory}/snippets/stubs</directory>
			<outputDirectory>customer-stubs/mappings</outputDirectory>
			<includes>
				<include>**/*</include>
			</includes>
		</fileSet>
		<fileSet>
			<directory>${basedir}/src/test/resources/contracts</directory>
			<outputDirectory>customer-stubs/contracts</outputDirectory>
			<includes>
				<include>**/*.groovy</include>
			</includes>
		</fileSet>
	</fileSets>
</assembly>

<!-- end of stub.xml-->

Gradle. 

task copyStubs(type: Copy, dependsOn: 'generateWireMockClientStubs') {
//    Preserve directory structure from 1.0.X of spring-cloud-contract
    from "${project.buildDir}/resources/main/customer-stubs/META-INF/${project.group}/${project.name}/${project.version}"
    into "${project.buildDir}/resources/main/customer-stubs"
}

12.2 1.1.x → 1.2.x

This section covers upgrading from version 1.1 to version 1.2.

12.2.1 Custom HttpServerStub

HttpServerStub includes a method that was not in version 1.1. The method is String registeredMappings() If you have classes that implement HttpServerStub, you now have to implement the registeredMappings() method. It should return a String representing all mappings available in a single HttpServerStub.

See issue 355 for more detail.

12.2.2 New packages for generated tests

The flow for setting the generated tests package name will look like this:

  • Set basePackageForTests
  • If basePackageForTests was not set, pick the package from baseClassForTests
  • If baseClassForTests was not set, pick packageWithBaseClasses
  • If nothing got set, pick the default value: org.springframework.cloud.contract.verifier.tests

See issue 260 for more detail.

12.2.3 New Methods in TemplateProcessor

In order to add support for fromRequest.path, the following methods had to be added to the TemplateProcessor interface:

  • path()
  • path(int index)

See issue 388 for more detail.

12.2.4 RestAssured 3.0

Rest Assured, used in the generated test classes, got bumped to 3.0. If you manually set versions of Spring Cloud Contract and the release train you might see the following exception:

Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:testCompile (default-testCompile) on project some-project: Compilation failure: Compilation failure:
[ERROR] /some/path/SomeClass.java:[4,39] package com.jayway.restassured.response does not exist

This exception will occur due to the fact that the tests got generated with an old version of plugin and at test execution time you have an incompatible version of the release train (and vice versa).

Done via issue 267

12.3 1.2.x → 2.0.x

12.3.1 No Camel support

We will add back Apache Camel support only after this issue gets fixed

13. Links

The following links may be helpful when working with Spring Cloud Contract Verifier: