This version is still in development and is not considered stable yet. For the latest stable version, please use spring-cloud-contract 4.1.5!

Stub Runner Core

The stub runner core runs stubs for service collaborators. Treating stubs as contracts of services lets you use stub-runner as an implementation of Consumer-driven Contracts.

Stub Runner lets you 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.

Retrieving stubs

You can pick from the following options of acquiring stubs:

Aether-based solution that downloads JARs with stubs from Artifactory or Nexus
Classpath-scanning solution that searches the classpath with a pattern to retrieve stubs
Writing 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.

Downloading Stubs

You can control the downloading of stubs with the stubsMode switch. It picks value from the StubRunnerProperties.StubsMode enumeration. You can use the following options:

StubRunnerProperties.StubsMode.CLASSPATH (default value): Picks stubs from the classpath
StubRunnerProperties.StubsMode.LOCAL: Picks stubs from a local storage (for example, .m2)
StubRunnerProperties.StubsMode.REMOTE: Picks stubs from a remote location

The following example picks stubs from a local location:

@AutoConfigureStubRunner(repositoryRoot="https://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), the classpath is scanned. Consider the following example:

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

You can add the dependencies to your classpath, as follows:

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.thing1</groupId>
    <artifactId>thing2</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.thing1:thing2:1.0.0:superstubs") {
    transitive = false
}

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

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

For com.example.thing1:thing2, the following locations are scanned:

/META-INF/com.example.thing1/thing2/*/.*
/contracts/com.example.thing1/thing2/*/.*
/mappings/com.example.thing1/thing2/*/.*

You have to explicitly provide the group and artifact IDs when you package the producer stubs.

To achieve proper stub packaging, the producer would set up the contracts as follows:

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

By using the Maven assembly plugin or the 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, the classpath gets scanned and you can profit from the messaging or HTTP stubs without the need to download artifacts.

Configuring HTTP Server Stubs

Stub Runner has a notion of a HttpServerStub that abstracts the underlying concrete implementation of the HTTP server (for example, WireMock is one of the implementations). Sometimes, you need to perform some additional tuning (which is concrete for the given implementation) of the stub servers. To do that, Stub Runner gives you the httpServerStubConfigurer property that is available in the annotation and the JUnit rule and is accessible through system properties, where you can provide your implementation of the org.springframework.cloud.contract.stubrunner.HttpServerStubConfigurer interface. The implementations can alter the configuration files for the given HTTP server stub.

Spring Cloud Contract Stub Runner comes with an implementation that you can extend for WireMock: org.springframework.cloud.contract.stubrunner.provider.wiremock.WireMockHttpServerStubConfigurer. In the configure method, you can provide your own custom configuration for the given stub. The use case might be starting WireMock for the given artifact ID, on an HTTPS port. The following example shows how to do so:

Example 1. WireMockHttpServerStubConfigurer implementation

@CompileStatic
static class HttpsForFraudDetection extends WireMockHttpServerStubConfigurer {

	private static final Log log = LogFactory.getLog(HttpsForFraudDetection)

	@Override
	WireMockConfiguration configure(WireMockConfiguration httpStubConfiguration, HttpServerStubConfiguration httpServerStubConfiguration) {
		if (httpServerStubConfiguration.stubConfiguration.artifactId == "fraudDetectionServer") {
			int httpsPort = TestSocketUtils.findAvailableTcpPort()
			log.info("Will set HTTPs port [" + httpsPort + "] for fraud detection server")
			return httpStubConfiguration
					.httpsPort(httpsPort)
		}
		return httpStubConfiguration
	}
}

You can then reuse it with the @AutoConfigureStubRunner annotation, as follows:

@AutoConfigureStubRunner(mappingsOutputFolder = "target/outputmappings/",
		httpServerStubConfigurer = HttpsForFraudDetection)

Whenever an HTTPS port is found, it takes precedence over the HTTP port.

Running stubs

This section describes how to run stubs. It contains the following topics:

HTTP Stubs
Viewing Registered Mappings
Messaging Stubs

HTTP Stubs

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

The following example defines a stub in JSON:

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

Viewing Registered Mappings

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

You can also use the mappingsOutputFolder property to dump the mappings to files. For the annotation-based approach, it would resembling the following example:

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

For the JUnit approach, it resembles the following example:

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

Then, if you check out the target/outputmappings folder, 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) the 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.