Testing

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Overview

Writing automated tests for Jenkins and its plugins is important to ensure that everything works as expected — in various scenarios, with multiple Java versions, and on different operating systems — while helping to prevent regressions from being introduced in later releases.

Whether you’re writing a new Jenkins plugin, or just looking to participate in the Jenkins project, this guide aims to cover everything you should need to get started writing various types of automated tests. Basic experience of writing Java-based tests with the JUnit test framework is assumed.

To make the development of tests simpler, Jenkins comes with a test harness, based on the JUnit test framework. This provides the following features:

  1. Automated setup and teardown of a Jenkins installation, allowing each test method to run in a clean, isolated environment.

  2. Helper classes and methods to simplify the creation of jobs, agents, security realms, SCM implementations and more.

  3. Declarative annotations to specify the environment a test method will use; for example, setting the JENKINS_HOME contents.

  4. Direct access to the Jenkins object model. This allows tests to assert directly against the internal state of Jenkins.

  5. HtmlUnit support, making it simple to test interaction with the web UI and other HTTP calls.

Setting Up

Dependencies

Jenkins Test Harness

By default, you don’t need to do anything to set up the Jenkins Test Harness for your plugin. All Jenkins plugins inherit from the plugin parent POM and therefore have the test harness dependency included automatically.

Similarly, JUnit is included as a dependency by the parent POM, so you don’t need to add it as a dependency.

Overriding the Test Harness Version

If you’re using version 2.3 or newer of the plugin parent POM, you can change the test harness version used by overriding the jenkins-test-harness.version property, if you need newer features. For example:

<project>
  …
  <properties>
    <jenkins-test-harness.version>2.34</jenkins-test-harness.version>
  </properties>

Working with Pipeline

You are encouraged to test that your plugin works with Pipeline. You can do so without making your plugin itself dependent on various Pipeline-related plugins; instead you can include these as test dependencies, so that they are only used when compiling and running test cases.

This is done by adding the minimum required Pipeline plugins to the <dependencies> section of your POM. The following list covers typical integration tests:

<dependency>
  <groupId>org.jenkins-ci.plugins.workflow</groupId>
  <artifactId>workflow-basic-steps</artifactId>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.jenkins-ci.plugins.workflow</groupId>
  <artifactId>workflow-cps</artifactId>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.jenkins-ci.plugins.workflow</groupId>
  <artifactId>workflow-durable-task-step</artifactId>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.jenkins-ci.plugins.workflow</groupId>
  <artifactId>workflow-job</artifactId>
  <scope>test</scope>
</dependency>

(You will also need to specify <version>s, unless you are using the BOM.)

Depending on Other Plugins

Any Jenkins plugins that you add as dependencies to your POM with <scope>test</scope> will be available in the Jenkins installations created while running test cases, or when using mvn hpi:run.

You can also apply the @WithPlugin annotation to individual test cases, but this is rarely required.

Source Code Location

The source code for your test cases should be placed in the standard location for Maven projects, i.e. under the src/test/java/ directory.

Examples

To see some working examples of plugin development, including use of JenkinsRule to test plugin code in the context of temporary Jenkins installations, try using one of the official archetypes.

Running Tests

From the Command Line

mvn test will run all test cases, report progress and results on the command line, and write those results to JUnit XML files following the pattern target/surefire-reports/TEST-<class name>.xml.

From an IDE

Most Java IDEs should be able to run JUnit tests and report on the results.

What to Test

Now that we can write a basic test, we should discuss what you should be testing…

TODO: Unit testing of your code, as much as possible. JenkinsRule testing: creating jobs that use your build steps, running them, asserting on the output

Common Patterns

This section covers patterns that you will commonly use in your test cases, plus scenarios that you should consider testing.

Configuration Round-trip Testing

For Freestyle jobs, where users have to configure projects via the web interface, if you’re writing a Builder, Publisher or similar, it’s a good idea to test that your configuration form works properly. The process to follow is:

  1. Start up a Jenkins installation and programmatically configure your plugin.

  2. Open the relevant configuration page in Jenkins via HtmlUnit.

  3. Submit the configuration page without making any changes.

  4. Verify that your plugin is still identically configured.

This can be done easily with the configRoundtrip convenience methods in JenkinsRule. Use archetypes to see examples.

Providing Environment Variables

In Jenkins, you can set environment variables on the Configure System page, which then become available during builds. To recreate the same configuration from a test method, you can do the following:

@Rule public JenkinsRule j = new JenkinsRule();

@Test public void someTest() {
  EnvironmentVariablesNodeProperty prop = new EnvironmentVariablesNodeProperty();
  EnvVars env = prop.getEnvVars();
  env.put("DEPLOY_TARGET", "staging");
  j.jenkins.getGlobalNodeProperties().add(prop);
  // …
}

Providing Test Data

In order to test parts of your plugin, you may want certain files to exist in the build workspace, or that Jenkins is configured in a certain way. This section covers various ways to achieve this using the Jenkins Test Harness.

Customizing the Build Workspace

Using a Dummy SCM

Freestyle projects typically check out code from an SCM before running the build steps, and the test harness provides a few dummy SCM implementations which make it easy to "check out" files into the workspace.

The simplest of these is the SingleFileSCM which, as its name suggests, provides a single file during checkout. For example:

@Rule public JenkinsRule j = new JenkinsRule();

@Test public void customizeWorkspaceWithFile() throws Exception {
  // Create a Freestyle project with a dummy SCM
  FreeStyleProject project = j.createFreeStyleProject();
  project.setScm(new SingleFileSCM("greeting.txt", "hello"));
  // …
}

Once a build of this project starts, the file greetings.txt with the contents hello will be added to the workspace during the SCM checkout phase.

There are additional variants of the SingleFileSCM constructor which let you create the file contents from a byte array, or by reading a file from the resources folder, or another URL source. For example:

import io.jenkins.myplugin;

// Reads the contents from `src/test/resources/io/jenkins/myplugin/test.json`
project.setScm(new SingleFileSCM("data.json", getClass().getResource("test.json")));

// Reads the contents from `src/test/resources/test.json` — note the slash prefix
project.setScm(new SingleFileSCM("data.json", getClass().getResource("/test.json")));

If you want to provide more than a single file, you can use ExtractResourceSCM, which will extract the contents of a given zip file into the workspace:

import io.jenkins.myplugin;

// Extracts `src/test/resources/io/jenkins/myplugin/files-and-folders.zip` into the workspace
project.setScm(new ExtractResourceSCM(getClass().getResource("files-and-folders.zip")));
Within a Pipeline

Pipeline projects don’t have the concept of a single SCM, like Freestyle projects do, but offer a variety of ways to places files into a workspace.

At its most simple, you can use the writeFile step from the Pipeline: Basic Steps plugin. For example:

@Rule public JenkinsRule j = new JenkinsRule();

@Test public void customizeWorkspace() throws Exception {
    // Create a new Pipeline with the given (Scripted Pipeline) definition
    WorkflowJob project = j.createProject(WorkflowJob.class);
    project.setDefinition(new CpsFlowDefinition("" +
        "node {" + (1)
        "  writeFile text: 'hello', file: 'greeting.txt'" +
        "  // …" +
        "}", true));
    // …
}
1 The node allocates a workspace on an agent, so that we have somewhere to write files to.

Alternatively, you can use the unzip step from the Pipeline Utility Steps plugin to copy multiple files and folders into the workspace.

First, add the plugin to your POM as a test dependency — you can find the groupId and artifactId values in the plugin POM:

<dependency>
  <groupId>org.jenkins-ci.plugins</groupId>
  <artifactId>pipeline-utility-steps</artifactId>
  <version>1.5.1</version>
  <scope>test</scope>
</dependency>

You can then write a test which starts by extracting that zip file. For example:

import io.jenkins.myplugin;

public class PipelineWorkspaceExampleTest {
  @Rule public JenkinsRule j = new JenkinsRule();

  @Test public void customizeWorkspaceFromZip() throws Exception {
      // Get a reference to the zip file from the `src/test/resources/io/jenkins/myplugin/files-and-folders.zip`
      URL zipFile = getClass().getResource("files-and-folders.zip");

      // Create a new Pipeline with the given (Scripted Pipeline) definition
      WorkflowJob project = j.createProject(WorkflowJob.class);
      project.setDefinition(new CpsFlowDefinition("" +
          "node {" + (1)
          "  unzip '" + zipFile.getPath() + "'" + (1)
          "  // …" +
          "}", true));
      // …
  }
}
1 The path to the zip file is dynamic, so we pass it into the Pipeline definition.
Using FilePath

TODO: Expand this section, and explain the below example.

FilePath workspace = j.jenkins.getWorkspaceFor(job);
FilePath report = workspace.child("target").child("lint-results.xml");
report.copyFrom(getClass().getResourceAsStream("lint-results_r20.xml"));

Customizing the JENKINS_HOME Directory

TODO: Write this section.

Using @LocalData

TODO: Properly write this section.

Runs a test case with a data set local to test method or the test class.

This recipe allows your test case to start with the preset HUDSON_HOME data loaded either from your test method or from the test class. For example, if the test method is org.acme.FooTest.bar(), then you can have your test data in one of the following places in resources folder (typically src/test/resources):

  • Under org/acme/FooTest/bar directory (that is, you’ll have org/acme/FooTest/bar/config.xml), in the same layout as in the real JENKINS_HOME directory.

  • In org/acme/FooTest/bar.zip as a zip file.

  • Under org/acme/FooTest directory (that is, you’ll have org/acme/FooTest/config.xml), in the same layout as in the real JENKINS_HOME directory.

  • In org/acme/FooTest.zip as a zip file.

Search is performed in this specific order. The fall back mechanism allows you to write one test class that interacts with different aspects of the same data set, by associating the dataset with a test class, or have a data set local to a specific test method. The choice of zip and directory depends on the nature of the test data, as well as the size of it.

Configuring an SCM

TODO: Write this section. You can create a Git repository during a test using @GitSampleRepoRule.

Using Agents

TODO: Creating fake agents.

Enabling security

TODO: Creating fake security realms. Using LocalData presets.

Verifying Logs

You can verify log messages using @LoggerRule. This can also be useful for temporarily enabling certain loggers during interactive testing. For example:

import java.util.logging.Level;
import org.junit.Rule;
import org.junit.Test;
import org.jvnet.hudson.test.LoggerRule;

import static org.hamcrest.Matchers.containsString;
import static org.junit.Assert.assertThat;
import static org.jvnet.hudson.test.LoggerRule.recorded;

public class MyTest {

  public @Rule LoggerRule l = new LoggerRule();

  @Test
  public void testLogs() throws Exception {
    l.capture(3).record("my.logger.name", Level.ALL);
    doThingThatLogs();
    assertThat(l, recorded(Level.INFO, containsString("Thing started successfully")));
  }
}

Increasing Tests Timeout

The default timeout for Jenkins integration tests is 180 seconds.

The tests that require more resources may fail on a slower computer.

To increase the timeout of the tests you can use the following commands: mvn -Djenkins.test.timeout=250 verify

Performance Testing

Starting from Jenkins Test Harness 2.50, the framework provides ways to run microbenchmarks using Java Microbenchmark Harness.

To use them in your plugin, please find documentation here:

Further Pipeline Testing

Testing Durable Pipeline Steps

TODO: RestartableJenkinsRule.

Further Patterns

Custom builder

Advanced and Tips etc.

References