Generating a JaCoCo code coverage report with Maven

I don't understand, I try to generate code coverage report with JaCoCo and Maven, the simplest.

I have the following plugin in my pom.xml :

<plugin>
    <groupId>org.jacoco</groupId>
    <artifactId>jacoco-maven-plugin</artifactId>
    <version>${jacoco.version}</version>
    <executions>
      <execution>
        <id>prepare-agent</id>
        <goals>
          <goal>prepare-agent</goal>
        </goals>
      </execution>
      <execution>
        <id>report</id>
        <phase>prepare-package</phase>
        <goals>
          <goal>report</goal>
        </goals>
      </execution>
      <execution>
        <id>post-unit-test</id>
        <phase>test</phase>
        <goals>
          <goal>report</goal>
        </goals>
        <configuration>
          <!-- Sets the path to the file which contains the execution data. -->

          <dataFile>target/jacoco.exec</dataFile>
          <!-- Sets the output directory for the code coverage report. -->
          <outputDirectory>target/my-reports</outputDirectory>
        </configuration>
      </execution>
    </executions>
    <configuration>
      <systemPropertyVariables>
        <jacoco-agent.destfile>target/jacoco.exec</jacoco-agent.destfile>
      </systemPropertyVariables>
  </configuration>
</plugin>

And when I try to do a mvn test, it just doesn't do anything. Not even an error or something. It say BUILD SUCESS for my tests but Maven seems to not see JaCoCo. If I try to execute mvn jacoco:report anyway I have a message : Skipping JaCoCo execution due to missing execution data file.

Solution

The following configuration should be enough:

<build>
  <plugins>
    <plugin>
      <groupId>org.jacoco</groupId>
      <artifactId>jacoco-maven-plugin</artifactId>
      <version>${jacoco.version}</version>
      <executions>
        <execution>
          <id>prepare-agent</id>
          <goals>
            <goal>prepare-agent</goal>
          </goals>
        </execution>
        <execution>
          <id>report</id>
          <phase>test</phase>
          <goals>
            <goal>report</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

The reports can then be found in target/site/jacoco/

Reasons why it does not work in your case:

The Plugin configuration is inside pluginManagement
The Plugin is inside a profile

Also check the maven log when you execute mvn test for jacoco-maven-plugin. For more information run mvn -X test