Maven multi module project with separate tests module - Code Coverage?

Question

I have a maven multi module project.

root:
    moduleA/   # no unit tests
    moduleB/   # no unit tests
    moduleC/   # no unit tests
    tests/     # All unit tests, since depends on modules A, B and C

All tests are in single module called tests/ and all code is in separate modules.

Is there a way I can get code coverage?

Answer 1

There is a way to accomplish this. The magic is to create a combined jacoco.exec file and to do it in two steps. My pom:

<properties>
    ...
    <jacoco.overall.exec>${maven.multiModuleProjectDirectory}/target/jacoco_analysis/jacoco.exec</jacoco.overall.exec>
</properties>

<build>
    <pluginManagement>
        <plugins>

            ...

            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.7.8</version>
                <configuration>
                    <destFile>${jacoco.overall.exec}</destFile>
                    <dataFile>${jacoco.overall.exec}</dataFile>
                </configuration>
            </plugin>

            ...

        </plugins>
    </pluginManagement>
</build>

<profiles>
    <profile>
        <id>runTestWithJacoco</id>
        <activation>
            <property>
                <name>runTestWithJacoco</name>
                <value>true</value>
            </property>
        </activation>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.jacoco</groupId>
                    <artifactId>jacoco-maven-plugin</artifactId>
                    <executions>
                        <execution>
                            <id>default-prepare-agent</id>
                            <goals>
                                <goal>prepare-agent</goal>
                            </goals>
                            <configuration>
                                <append>true</append>
                            </configuration>
                        </execution>
                    </executions>
                </plugin>
            </plugins>
        </build>
    </profile>
    <profile>
        <id>createJacocoReport</id>
        <activation>
            <property>
                <name>createJacocoReport</name>
                <value>true</value>
            </property>
        </activation>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.jacoco</groupId>
                    <artifactId>jacoco-maven-plugin</artifactId>
                    <executions>
                        <execution>
                            <id>default-report</id>
                            <phase>validate</phase>
                            <goals>
                                <goal>report</goal>
                            </goals>
                        </execution>
                    </executions>
                </plugin>
            </plugins>
        </build>
    </profile>
</profiles>

Add this to your parent pom and execute mvn clean install -DrunTestWithJacoco and than mvn validate -DcreateJacocoReport. Now you have the complete coverage of a class and it doesn't matter which test covered it. The magic is to use maven.multiModuleProjectDirectory to create a combined jacoco.exec file. This property is available since maven 3.3.1 and points to the folder where you started your maven build.