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Docker Test Runner Gradle Plugin

Circle CI

This plugin provides a simple way to test Gradle projects in multiple different environments specified in Dockerfiles as part of a build. Given a set of Dockerfiles that contain the desired environments, this plugin adds tasks for running the project's tests and coverage tasks in those containers. The test and coverage output for each environment is persisted separately, and it is possible to combine the coverage from the tests run in all of the environments using gradle-jacoco-coverage.

This plugin makes it trivial to test existing projects against multiple different environments in a lightweight manner. The ability to easily run tests in different environments locally makes the development process faster and allows environment verification to be part of the core build. It also allows code coverage to properly account for code that will only execute in certain environments.

An example use case of this plugin is testing a project against multiple different versions or vendors of a JDK.


Apply the plugin using standard gradle convention:

plugins {
    id 'com.palantir.docker-test-runner'

Because this plugin adds test and coverage tasks, it requires the 'java' and 'jacoco' plugins to already be applied.

Configure the plugin using the 'dockerTestRunner' block. The simplest way to configure the plugin is to specify a FileCollection of Dockerfiles that should be used as the test environments:

dockerTestRunner {
    dockerFiles fileTree(project.rootDir) {
        include '**/Dockerfile'

The dockerTestRunner block offers the following options:

  • dockerFiles: adds the specified Dockerfiles to use as test environments.
  • dockerRunner: adds the provided runner to use as a test environment. This method takes a map with the following properties:
    • dockerFile: the File for the test environment being added.
    • (optional) name the name of the test environment. If it is not provided, then a default name is generated based on the path of the file.
    • (optional) testConfig configuration object for this runner that contains runArgs, testConfig and jacocoConfig`. The runner-specific configuration is applied in addition to the top-level configuration. See description of top-level options for explanation of these options.
  • (optional) runArgs is a Multimap that can be provided with custom arguments that should be provided to the Docker run commmand that is executed by the task. The keys are the flags and the values are the values for the flag.
  • (optional) testConfig is a closure that can be used to configure the Test task run in the container. The closure's delegate is set to be the Test task, so Test properties such as classpath and reports can be configured using this closure.
  • (optional) jacocoConfig is a closure that can be used to configure the Jacoco task run in the container. The closure's delegate is set to be the JacocoReport task, so Jacoco properties such as executionData and sourceDirectories` can be configured using this closure.
  • (optional) createGradleCacheVolumeImage specifies the image that should be used by the createGradleCacheVolume task. If it is null, then the image of the first specified dockerRunner will be used.

Configuration Examples

Add all Dockerfile files as test environments and configure tests to only run tests in a specific directory:

dockerTestRunner {
    dockerFiles fileTree(project.rootDir) {
        include '**/Dockerfile'

    testConfig = {

Add 2 separate named test environments with custom test configurations and global coverage configuration:

dockerTestRunner {
    dockerRunner name: 'openjdk-7',
                 dockerFile: file('dockerFiles/openjdk-7.dockerfile'),
                 testConfig: {

    dockerRunner name: 'openjdk-8',
                 dockerFile: file('dockerFiles/openjdk-8.dockerfile'),
                 testConfig: {

    jacocoConfig = {
        classDirectories = project.files(classDirectories.files.collect {
            project.fileTree(dir: it, exclude: '**/Immutable*.class')


Each environment has a name that is either specified as the runner's name or derived from the parent directory and name of its Dockerfile.

Each environment has its own task group that contains 3 tasks:

  • buildDockerTestRunner-{name}
  • runJacocoTestReportDockerTestRunner-{name} (if the Jacoco plugin is applied to the project)
  • runTestDockerTestRunner-{name}

If there is at least one environment, then the following bulk tasks that run the tasks for all of the environments are added:

  • buildDockerTestRunner
  • createGradleCacheVolume
  • jacocoTestReportDockerTestRunner (if the Jacoco plugin is applied to the project)
  • removeGradleCacheVolume
  • testDockerTestRunner


The build tasks run docker build to create the images for the environments. The build tasks are invoked automatically as needed, but can be called directly to build the images for caching purposes.


The test tasks use docker run to run a Docker container of the image for the specified environment and then runs a Gradle test task within that container. The test task that is run within the container tests all of the classes in the project's Gradle test output classes directory using the test runtime path.

The default destination for the XML and HTML reports will be the same destination used by the standard Gradle test task with the name appended to it. For example, if the regular test tasks writes its output to 'build/reports/tests', then this test task will write its output to 'build/reports/tests-{name}'. The raw Jacoco execution output is written to "${project.getBuildDir()}/jacoco/${name}.exec". This task can be modified or configured using the testConfig closure.

Jacoco Test Report

The Jacoco test report tasks will be present only if the jacoco plugin is applied to the project. These tasks are analogous to the test tasks, but generate a coverage report rather than runningtests. The default output location of the coverage reports is the same location used by the standard Gradle Jacoco reports task, but the name of the directory within the reports directory will be the test environment name. This task can be modified or configured using the jacocoConfig closure.

Create Gradle Cache Volume

This tasks creates the Gradle cache Docker data volume and copies the content of the current Gradle user home directory into the data volume. This data volume is shared by all subprojects in a given Gradle project. The image that is used to perform the copy operation can be specified using the createGradleCacheVolumeImage property (by default, the image file of the first specified dockerRunner will be used). The image being used must already be built/present -- if a custom image is being used, ensure that it is built using the appropriate build task before invoking this task. This task typically only needs to be run in CI environments.

In order to increase performance, the Docker test containers use a Docker data volume as the Gradle user home (the Gradle cache). The data volume is created by a container if it does not already exist. This means that, the first time a test container runs, it may need to download the Gradle dependencies into the cache. In local environments, incurring this one-time cost typically is not an issue because the data volume will persist. However, in CI environments this can be costly. In those scenarios, this task can be run before the other test tasks are run to copy the local Gradle cache into the Gradle cache Docker volume.

Note that this task copies the entire contents of the Gradle user home directory, so if that directory is large (as it can be in local environments) this task may take a long time. This task should generally not be used if the local Gradle user home cache is large.

Remove Gradle Cache Volume

Removes the Gradle cache Docker data volume using the docker volume rm command. Note that the docker volume command only exists in Docker 1.9.0 and later. This task will fail if the docker volume command is not available locally or if the volume could not be removed because it is in use by a container.

Combining Coverage

The coverage outputs of multiple different test environments can be combined using gradle-jacoco-coverage without any further modifications. Running that plugin's jacocoFullReport task will create a report that includes the coverage outputs of the tests run in the Docker environments.

In addition to creating these scripts, this plugin will merge the entire contents of ${projectDir}/service and ${projectDir}/var into the package.


This plugin is made available under the Apache 2.0 License.


Gradle plugin for running tests in Docker environments








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