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There are two different ways to feed Sonar SonarQube with information on unit tests execution and code coverage:

• Using its embedded engine to let Sonar SonarQube directly launch the unit tests execution and code coverage. Then, the analyzer will automatically fed the database with data exported from the generated reports.
• Reusing existing reports that have been previously generated by external tools.

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Using SonarQube Embedded Engine

Maven supports this mode with the following code coverage tools: JaCoCo, Cobertura, Emma and Clover.

The Sonar SonarQube Ant Task and the Sonar SonarQube Runner do not support this mode.

First, tell Sonar SonarQube to execute the unit tests and the code coverage tool:

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With Maven, then, you just have to tell Sonar SonarQube which code coverage engine you wish to use: jacoco or cobertura or emma or clover.

<sonar.java.coveragePlugin>jacoco or cobertura or emma or clover</sonar.java.coveragePlugin>
 
Prior to SonarSonarQube 3.4, the property was sonar.core.codeCoveragePlugin.

Note that this property can be set at Sonar SonarQube instance level through the web interface: Settings > Configuration > General Settings > Java.

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Sample projects are available on github that can be browsed or downloaded: projects/code-coverage/combined ut-it/maven/combined-ut-it-multimodule-maven-jacoco

Note that this project structure is not compatible with the below feature: mapping of unit tests and covered code.

Mapping of Unit Tests and Covered Code

Since SonarQube 3.5, it is possible to display the mapping of unit tests and covered code. The objective is to answer the following questions:

• Which files are covered by a given unit test?
• How many lines of code are covered by a given unit test?
• Which lines are covered by a given unit test?
• Which tests do cover a given line of code?

A sample project is available on github that can be browsed or downloaded: projects/code-coverage/ut/maven/ut-maven-jacoco-runTests. What is necessary to get this mapping is contained between 'BEGIN/END: Specific to mapping unit tests and covered code' tags in the pom file. Note that you have to run the analysis with the 'coverage-per-test' profile. Read the README file for more information.

Requires:

• JUnit 4.7+
• Maven Surefire Plugin 2.4+

Reusing Existing Reports

Every analyzer supports this reusing reports mode.

To be reused by Sonar SonarQube :

• The tests execution reports have to comply to the JUnit XML format.
• The code coverage reports have to be generated by either JaCoCo, Emma, Cobertura or Clover.

First, tell Sonar SonarQube to reuse existing reports:

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<property name="sonar.dynamicAnalysis" value="reuseReports" />

With Sonar Runner SonarQubeRunner in your sonar-project.properties file:

sonar.dynamicAnalysis=reuseReports

Test Execution Reports

Tell Sonar SonarQube where your unit tests execution reports are: absolute or relative path to the directory containing your reports

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<property name="sonar.surefire.reportsPath" value="[baseDir]/myReports/myExecutionReports" />

With Sonar SonarQube Runner in your sonar-project.properties file:

sonar.surefire.reportsPath=[baseDir]/myReports/myExecutionReports

Code Coverage Report 

First, tell Sonar SonarQube which code coverage engine has been used to generate the reports: jacoco or cobertura or emma or clover.

<sonar.java.coveragePlugin>jacoco or cobertura or emma or clover</sonar.java.coveragePlugin>
 
Prior to SonarSonarQube 3.4, the property was sonar.core.codeCoveragePlugin.

Then, tell Sonar SonarQube where to get the code coverage reports:

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<property name="sonar.jacoco.reportPath" value="[baseDir]/myReports/myCodeCoverageReport" />

With Sonar Runner SonarQubeRunner in your sonar-project.properties file:

sonar.jacoco.reportPath=[baseDir]/myReports/myCodeCoverageReport

Depending on the code coverage tool you used to generate your report, replace jacoco by emma, cobertura or clover in the property name.

See also the Manage Code Coverage by Unit Tests with Sonar blog post.

FAQ

0% code coverage reported whereas unit tests are correctly executed

This problem occurs while using the Maven Cobertura Plugin and a special configuration of the Maven Surefire Plugin preventing unit tests to be forked. This problem can be solved by removing the line "<forkMode>never</forkMode>" in the Maven configuration file (see SONAR-1445 and MCOBERTURA-70).

java.lang.Error: Unable to access JaCoCo Agent - make sure that you use JaCoCo and version not lower than 0.6.2

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<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>2.4.2</version>
  <configuration>
    <forkMode>never</forkMode> <!-- Do not set forkMode to never -->
    <reportFormat>xml</reportFormat>
    <testFailureIgnore>true</testFailureIgnore>
  </configuration>
</plugin>
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• Make sure that you call first mvn clean install and then mvn sonar:sonar Pcoverage-per-test separately. Indeed, only SonarQube can attach the JaCoCo agent, so mvn clean install sonar:sonar -Pcoverage-per-test will produce the error because the test phase will be executed a first time alone.