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Execute Functional Tests in a Docker Container with Gradle (Part 2)

25 November 2014

In part one of this blog post, I discussed how to build a functional test using Spock and Gradle. Normally, this is all that you would need to be able to test the part of your application that relies on a data source. However, what can you do if you find yourself in a situation where you do not have access to dependencies or the repositories that provide them? The solution is to bundle your tests along with the dependencies and execute them as an application. In this post, I will discuss how I accomplished such a solution using Gradle and Docker. First, let’s look at the Gradle build script:

apply plugin: 'groovy'
apply plugin: 'jetty'

ext {
    webSourceDir = "$buildDir/www"
    imageName = "${rootProject.name}-functional-tests"
    springVersion = '4.0.7.RELEASE'
}

sourceSets {
    funcTest {
        groovy {
            srcDir file('src/functionalTest/groovy')
        }
    }
}

eclipse {
    classpath {
        downloadSources = true
        defaultOutputDir = file("$buildDir/classes")
    }
    project {
        name = "${rootProject.name}-functional-tests"
    }
}

eclipseJdt.enabled = false
cleanEclipseJdt.enabled = false

jettyRun {
    httpPort = System.getenv('PORT') ? System.getenv('PORT') as int : 8080
    contextPath = 'status/check'
    webAppSourceDirectory = file(webSourceDir)
}

dependencies {
    compile project(':app')		// include the code that is needed to execute the tests (e.g., any entity classes, etc)

    testCompile 'junit:junit:4.11'
    testCompile 'cglib:cglib-nodep:3.1'
    testCompile 'org.objenesis:objenesis:2.1'
    testCompile 'org.spockframework:spock-core:0.7-groovy-2.0'
    testCompile 'org.spockframework:spock-spring:0.7-groovy-2.0'
    testCompile "org.springframework:spring-test:${springVersion}"

    funcTestCompile sourceSets.main.output
    funcTestCompile configurations.testCompile
    funcTestRuntime configurations.testRuntime
}

task buildDist(type: Tar, group:'Build', description: 'Builds the Tar distribution of the project.') {
    archiveName = "${rootProject.name}-functional-tests.tar"
    from('bin') {
        into('bin')
    }
    from(rootProject.projectDir) {
        exclude('**/build/**')
        exclude('**/*.tar')
        exclude('**/.gradle/**')
    }
}

task funcTest(type: Test, group:'Verification', description: 'Runs the functional tests.') {
    testClassesDir = sourceSets.funcTest.output.classesDir
    classpath = sourceSets.funcTest.runtimeClasspath
    jvmArgs = ['-Duser.timezone=UTC']
    environment = [:] // any necessary env vars for the test
}

task resolveDependencies {
    doLast {
        project.rootProject.allprojects.each { subProject ->
            subProject.buildscript.configurations.each { configuration ->
                configuration.resolve()
            }
            subProject.configurations.each { configuration ->
                configuration.resolve()
            }
        }
    }
}

task createWebSourceDir {
    doLast {
        new File(webSourceDir).mkdirs()
    }
}

task collectTestResults(type:Tar, group:'Verification', dependsOn:['createWebSourceDir', 'funcTest'], description: 'Generates a tarball of the collected test report.') {
    archiveName = 'functional-test-reports.tar'
    destinationDir = file(webSourceDir)
    from("$buildDir/reports/tests") {
        into('reports/tests')
    }
    from("$buildDir/test-results") {
        into('test-results')
    }
}

task execute(dependsOn:['jettyRun'])

/*
 * Ensure that the tests are always executed
 */
project.tasks.collectTestResults.outputs.upToDateWhen { false }
project.tasks.funcTest.outputs.upToDateWhen { false }
project.tasks.resolveDependencies.outputs.upToDateWhen { false }
build.finalizedBy(project.tasks.buildDist)
project.tasks.buildDist.dependsOn(['build'])
project.tasks.jettyRun.dependsOn(['collectTestResults'])

The script above has three very interesting parts:

  • A custom test task that runs all of the functional tests defined by the funcTest configuration.

  • The inclusion of the Gradle Jetty Plugin to expose the test reports.

  • A custom task (resolveDependencies) that will ensure that all the required dependencies are resolved and included when building the Docker image.

Now let’s look at the Dockerfile for the functional tests before tying it all together. Below is a simple Dockerfile:

FROM registry.hub.docker.com/your-base-image:latest

# Install the functional tests
RUN mkdir /var/tests
ADD build/distributions/my-functional-tests.tar /var/tests
RUN chmod +x /var/tests/bin/functional-tests.sh

# Force Gradle to download all of its dependencies at image build time!
RUN rm -rf /root/.gradle
RUN cd /var/tests && ./gradlew --refresh-dependencies resolveDependencies > /dev/null

EXPOSE 8080
CMD ["cd /var/tests && ./gradlew --offline clean execute"]

The Dockerfile extracts the contents of the TAR into the /var/tests folder inside the Docker image. Once extracted, the Dockerfile also invokes the resolveDepednencies custom task that we saw in the Gradle build script above. Because the Docker image is being built on a machine that has access to our dependency repositories, it can resolve everything needed at image creation time. By resolving the dependencies at this point, we guarantee that the dependencies have been downloaded and cached by Gradle inside of the Docker image. The final piece of the puzzle is the CMD directive, which runs the custom execute task from the Gradle build script. As we saw above, the execute task launches Jetty, which in turn launches the functional tests via the Gradle task dependency set up in the script. Upon successful completion of the tests, the test reports generated by Gradle are exposed by Jetty so that they can be viewed/copied/etc. By tying all of these pieces together, we have created a stand-alone Docker image capable of executing functional tests using Gradle in an environment that does not have the ability to resolve dependencies!

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