JaCoCo coverage visualization

Use JaCoCo coverage reports to display line-by-line coverage annotations in merge request diffs. GitLab reads the JaCoCo XML report and annotates each changed line as covered (green) or not covered (red).

Coverage visualization uses the artifacts:reports:coverage_report keyword. It does not display a coverage percentage in the MR widget or populate coverage history graphs. To display a coverage percentage, configure the coverage keyword separately.

Add a JaCoCo coverage job

Add a JaCoCo coverage job when you want to display line-by-line coverage annotations in merge request diffs.

Prerequisites:

• A properly formatted JaCoCo XML file that provides line coverage.

To add a JaCoCo coverage job:

1. Add a job to your .gitlab-ci.yml file with artifacts:reports:coverage_report set to jacoco. For example:

   test-jdk11:
     stage: test
     image: maven:3.6.3-jdk-11
     script:
       - mvn $MAVEN_CLI_OPTS clean org.jacoco:jacoco-maven-plugin:prepare-agent test jacoco:report
     artifacts:
       reports:
         coverage_report:
           coverage_format: jacoco
           path: target/site/jacoco/jacoco.xml

2. Set path to the location of the generated JaCoCo XML report.

If the job generates multiple reports, use a wildcard in the artifact path.

Coverage indicators

JaCoCo visualization uses instructions (C0 Coverage), represented as ci (covered instructions) in reports.

After the pipeline completes, coverage displays in the merge request diff view with these indicators:

• Instructions covered (green): lines with at least one covered instruction (ci > 0)
• No instructions covered (red): lines without any covered instructions (ci = 0)
• No coverage information: lines not included in the coverage report

For example, with this report output:

<line nr="83" mi="2" ci="0" mb="0" cb="0"/>
<line nr="84" mi="2" ci="0" mb="0" cb="0"/>
<line nr="85" mi="2" ci="0" mb="0" cb="0"/>
<line nr="86" mi="2" ci="0" mb="0" cb="0"/>
<line nr="88" mi="0" ci="7" mb="0" cb="1"/>

The merge request diff view displays coverage as follows:

In this example, lines 83-86 show red bars for uncovered code, line 88 shows a green bar for covered code, and lines 87, 89-90 have no coverage data.

Troubleshooting

For troubleshooting coverage visualization, including path resolution failures and annotations that do not appear as expected, see coverage visualization troubleshooting.

Give feedback

JaCoCo coverage visualization is actively being improved. To report issues or suggest improvements, leave your feedback in issue 479804.