GitHub - dingsl1988/spring-cloud-contract: Support for Consumer Driven Contracts in Spring

Spring Cloud Contract

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

Spring Cloud Contract workshops

If you prefer to learn about the project by doing some tutorials, you can check out the workshops under this link.

Spring Cloud Contract Verifier

Spring Cloud Contract Verifier Introduction

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.

Why a Contract Verifier?

Assume that we have a system consisting of multiple microservices:

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.

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.

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

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.

How It Works

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

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.*`
 */

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"}, workOffline = true)
@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.

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");
}

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

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" }
}

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:

Start doing TDD by writing a test for your feature.
Write the missing implementation.
Clone the Fraud Detection service repository locally.
Define the contract locally in the repo of Fraud Detection service.
Add the Spring Cloud Contract Verifier plugin.
Run the integration tests.
File a pull request.
Create an initial implementation.
Take over the pull request.
Write the missing implementation.
Deploy your app.
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

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	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"}, workOffline = true)
@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.

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

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.

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 switch off the value of the workOffline parameter in your annotation. 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!

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.

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.

Spring Cloud Contract video

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

Readings

Samples

You can find some samples at samples.

Links

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

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.

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	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.

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	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.

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 followin 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.

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.

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).

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	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.

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

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.

Documentation

You can read more about Spring Cloud Contract Verifier by reading the {documentation_url}[docs]

Contributing

Spring Cloud is released under the non-restrictive Apache 2.0 license, and follows a very standard Github development process, using Github tracker for issues and merging pull requests into master. If you want to contribute even something trivial please do not hesitate, but follow the guidelines below.

Sign the Contributor License Agreement

Before we accept a non-trivial patch or pull request we will need you to sign the Contributor License Agreement. Signing the contributor’s agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do. Active contributors might be asked to join the core team, and given the ability to merge pull requests.

Code of Conduct

This project adheres to the Contributor Covenant code of conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to spring-code-of-conduct@pivotal.io.

Code Conventions and Housekeeping

None of these is essential for a pull request, but they will all help. They can also be added after the original pull request but before a merge.

Use the Spring Framework code format conventions. If you use Eclipse you can import formatter settings using the eclipse-code-formatter.xml file from the Spring Cloud Build project. If using IntelliJ, you can use the Eclipse Code Formatter Plugin to import the same file.
Make sure all new .java files to have a simple Javadoc class comment with at least an @author tag identifying you, and preferably at least a paragraph on what the class is for.
Add the ASF license header comment to all new .java files (copy from existing files in the project)
Add yourself as an @author to the .java files that you modify substantially (more than cosmetic changes).
Add some Javadocs and, if you change the namespace, some XSD doc elements.
A few unit tests would help a lot as well — someone has to do it.
If no-one else is using your branch, please rebase it against the current master (or other target branch in the main project).
When writing a commit message please follow these conventions, if you are fixing an existing issue please add Fixes gh-XXXX at the end of the commit message (where XXXX is the issue number).

How to build it

Important

You need to have all the necessary Groovy plugins installed for your IDE to properly resolve the sources. For example in Intellij IDEA having both Eclipse Groovy Compiler Plugin & GMavenPlus Intellij Plugin results in properly imported project.

Project structure

Here you can find the Spring Cloud Contract folder structure

├── samples
├── scripts
├── spring-cloud-contract-dependencies
├── spring-cloud-contract-spec
├── spring-cloud-contract-starters
├── spring-cloud-contract-stub-runner
├── spring-cloud-contract-tools
├── spring-cloud-contract-verifier
├── spring-cloud-contract-wiremock
└── tests

samples - folder contains test samples together with standalone ones used also to build documentation
scripts - contains scripts to build and test Spring Cloud Contract with Maven, Gradle and standalone projects
spring-cloud-contract-dependencies - contains Spring Cloud Contract BOM
spring-cloud-contract-starters - contains Spring Cloud Contract Starters
spring-cloud-contract-spec - contains specification modules (contains concept of a Contract)
spring-cloud-contract-stub-runner - contains Stub Runner related modules
spring-cloud-contract-tools - Gradle and Maven plugin for Spring Cloud Contract Verifier
spring-cloud-contract-verifier - core of the Spring Cloud Contract Verifier functionality
spring-cloud-contract-wiremock - all WireMock related functionality
tests - integration tests for different messaging technologies

Commands

To build the core functionality together with Maven Plugin you can run

./mvnw clean install -P integration

Calling that function will build core, Maven plugin, Gradle plugin and run end to end tests on the standalone samples in proper order (both for Maven and Gradle).

To build the Gradle Plugin only

cd spring-cloud-contract-tools/spring-cloud-contract-gradle-plugin
./gradlew clean build

Helpful scripts

We’re providing a couple of helpful scripts to build the project.

To build the project in parallel (by default uses 4 cores but you can change it)

./scripts/parallelBuild.sh

and with 8 cores

CORES=8 ./scripts/parallelBuild.sh

To build the project without any integration tests (by default uses 1 core)

./scripts/noIntegration.sh

and with 8 cores

CORES=8 ./scripts/noIntegration.sh

To generate the documentation (both the root one and the maven plugin one)

./scripts/generateDocs.sh

Name		Name	Last commit message	Last commit date
Latest commit History 1,755 Commits
.circleci		.circleci
.mvn		.mvn
config		config
docs		docs
samples		samples
scripts		scripts
spring-cloud-contract-dependencies		spring-cloud-contract-dependencies
spring-cloud-contract-shade		spring-cloud-contract-shade
spring-cloud-contract-spec		spring-cloud-contract-spec
spring-cloud-contract-starters		spring-cloud-contract-starters
spring-cloud-contract-stub-runner		spring-cloud-contract-stub-runner
spring-cloud-contract-tools		spring-cloud-contract-tools
spring-cloud-contract-verifier		spring-cloud-contract-verifier
spring-cloud-contract-wiremock		spring-cloud-contract-wiremock
tests		tests
.gitignore		.gitignore
.settings.xml		.settings.xml
LICENSE		LICENSE
README.adoc		README.adoc
asciidoctor.css		asciidoctor.css
circle.yml		circle.yml
ideas.md		ideas.md
mvnw		mvnw
mvnw.cmd		mvnw.cmd
pom.xml		pom.xml

License

dingsl1988/spring-cloud-contract

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Spring Cloud Contract

Spring Cloud Contract workshops

Spring Cloud Contract Verifier

Spring Cloud Contract Verifier Introduction

Why a Contract Verifier?

Testing issues

Purposes

How It Works

Defining the contract

Client Side

Server Side

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

Technical note

Consumer side (Loan Issuance)

Producer side (Fraud Detection server)

Consumer Side (Loan Issuance) Final Step

Dependencies

Additional Links

Spring Cloud Contract video

Readings

Samples

Links

Spring Cloud Contract WireMock

Spring Cloud Contract WireMock

Registering Stubs Automatically

Using Files to Specify the Stub Bodies

Alternative: Using JUnit Rules

Relaxed SSL Validation for Rest Template

WireMock and Spring MVC Mocks

Generating Stubs using REST Docs

Generating Contracts by Using REST Docs

Documentation

Contributing

Sign the Contributor License Agreement

Code of Conduct

Code Conventions and Housekeeping

How to build it

Project structure

Commands

Helpful scripts

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