Java Test Coverage

SonarCloud supports the reporting of test coverage as part of the analysis of your Java project. 

However, SonarCloud does not produce the coverage report itself. Instead, you must set up a third-party tool to produce the report as part of your build process. You then need to configure your analysis to tell the SonarScanner where the report is located so that it can pick it up and send it to SonarCloud, where it will be displayed on your project dashboard along with the other analysis metrics.

For Java projects, SonarCloud directly supports the JaCoCo coverage tool (see Generic Test Data for information on integrating other coverage tools).

Follow the tutorial

When you import your Java project into SonarCloud you will be guided through the setup process by an in-product tutorial. Follow the tutorial specific to your CI. When it asks, What option best describes your build?, choose Maven or Gradle, depending on which you are using. When you are done with the tutorial, you should have a functioning CI-based analysis setup for your Java project. The next step is to adjust it to get coverage working. 

Adjust your setup

To enable coverage you need to:

  • Adjust your build process so that JaCoCo report generation step runs before the SonarScanner step.
  • Make sure that JacCoCo writes its report file to a defined path in the build environment.
  • Configure the scanning step of your build so that the SonarScanner picks up the report file from that defined path.

Add coverage in a single-module Maven project

To add coverage to your Maven project you need to use the jacoco-maven-plugin and its report goal to create a code coverage report. 

Typically, you would create a specific Maven profile for executing the unit tests with instrumentation and producing the coverage report only on demand. 

In the most basic case, we will need to execute two goals: jacoco:prepare-agent, which allows coverage info to be collected during unit tests execution, and jacoco:report, which uses data collected during unit test execution to generate a report. By default, the tool generates XML, HTML, and CSV versions of the report. Here, we explicitly specify XML, since that is the only one we need for SonarCloud.

${project.basedir}/pom.xml

<profile>
  <id>coverage</id>
  <build>
   <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
     <artifactId>jacoco-maven-plugin</artifactId>
      <version>0.8.7</version>
      <executions>
        <execution>
          <id>prepare-agent</id>
          <goals>
            <goal>prepare-agent</goal>
          </goals>
        </execution>
        <execution>
          <id>report</id>
          <goals>
            <goal>report</goal>
          </goals>
          <configuration>
            <formats>
              <format>XML</format>
            </formats>
          </configuration>
        </execution>
      </executions>
    </plugin>
   </plugins>
  </build>
</profile>

By default the generated report will be saved under target/site/jacoco/jacoco.xml. This location will be checked automatically by the scanner, so no further configuration is required. Just launch: 

mvn sonar:sonar -Pcoverage

as usual and the report will be picked up.

If you need to change the directory where the report is generated, you can set the property either on the command line using Maven’s -D switch.

mvn -Dsonar.coverage.jacoco.xmlReportPaths=
      ../app-it/target/site/jacoco-aggregate/jacoco.xml
    sonar:sonar -Pcoverage

or in your pom.xml:

${project.basedir}/pom.xml


<properties>
  <sonar.coverage.jacoco.xmlReportPaths>
    ../app-it/target/site/jacoco-aggregate/jacoco.xml
  </sonar.coverage.jacoco.xmlReportPaths>
</properties>

Wildcards and a comma-delimited list of paths are supported. See Coverage Analysis Parameters for details. The path can be either absolute or relative to the project root.

Add coverage in a multi-module Maven project

For multi-module Maven projects, you configure the jacoco-maven-plugin in a profile in the parent pom just as in the single module case, above. By default, a separate coverage report will be generated for each module.

If you want to aggregate all the module-specific reports into one project-level report, the easiest solution is to create a special Maven module (alongside the ones you already have), that contains nothing except a pom.xml that uses the report-aggregate goal. Here is an example:

${project.basedir}/report-aggregate-module/pom.xml

<project>
  <artifactId>my-project-report-aggregate</artifactId>
  <name>My Project</name>
  <description>Aggregate Coverage Report</description>
  <dependencies>
    <dependency>
      <groupId>${project.groupId}</groupId>
      <artifactId>my-module-1</artifactId>
      <version>${project.version}</version>
    </dependency>
    <dependency>
      <groupId>${project.groupId}</groupId>
      <artifactId>my-module-2</artifactId>
      <version>${project.version}</version>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <executions>
          <execution>
            <id>report-aggregate</id>
            <phase>verify</phase>
            <goals>
              <goal>report-aggregate</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

When you invoke maven clean verify in the report-aggregate-module directory the aggregated report will be generated and placed inside that directory at the standard location target/site/jacoco-aggregate/jacoco.xml. Then, in the top level pom.xml you set sonar.coverage.jacoco.xmlReportPaths to this location:

${project.basedir}/pom.xml

<properties>/
  <sonar.coverage.jacoco.xmlReportPaths>
    ${project.basedir}/report-aggregate/target/site/
      jacoco-aggregate/jacoco.xml
  </sonar.coverage.jacoco.xmlReportPaths>
</properties>

Wildcards and a comma-delimited list of paths are supported. See Test Coverage Parameters for details.

Add coverage in a Gradle project

To set up code coverage for your Gradle files, you just need to apply the JaCoCo plugin together with the SonarScanner for Gradle to the build.gradle file of your project as the JaCoCo is already integrated into the default gradle distribution. 

${project.basedir}/build.gradle


plugins {
    id "jacoco"
    id "org.sonarqube" version "3.3”
}
 
jacocoTestReport {
    reports {
        xml.enabled true
    }
}

Your report will be automatically saved in the build/reports/jacoco directory. The sonarqube plugin automatically detects this location so no further configuration is required. To import coverage, launch:

  gradle test jacocoTestReport sonarqube

For more details, see the Gradle JaCoCo Plugin documentation.

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