Apache Maven PMD Plugin – Using a different ruleset for tests

Using a different ruleset for tests

PMD shall be configured to scan test source code with a less strict ruleset than production code. This can be achieved by configuring multiple plugin executions with different configurations.

Note: There are different opinions whether one should lower that quality just because it's "just test code". While test code doesn't run in production, it's used to test production code, so you might consider the test code then as your weakest link if you use less strict checks.

Here's the complete plugin configuration for this scenario:

<project>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-pmd-plugin</artifactId>
        <version>3.23.0</version>
        <configuration>
            <includeTests>false</includeTests>
            <rulesets>
                <ruleset>config/pmd/pmdMain.xml</ruleset>
            </rulesets>
            <linkXRef>false</linkXRef>
        </configuration>
        <executions>
            <execution>
                <id>pmd-main</id>
                <phase>verify</phase>
                <goals>
                    <goal>check</goal>
                </goals>
            </execution>
            <execution>
                <id>pmd-test</id>
                <phase>verify</phase>
                <goals>
                    <goal>pmd</goal>
                    <goal>check</goal>
                </goals>
                <configuration>
                    <targetDirectory>${project.build.directory}/pmdTest/</targetDirectory>
                    <includeTests>true</includeTests>
                    <excludeRoots>
                        <excludeRoot>${basedir}/src/main/java</excludeRoot>
                    </excludeRoots>
                    <rulesets>
                        <ruleset>config/pmd/pmdTest.xml</ruleset>
                    </rulesets>
                </configuration>
            </execution>
            <execution>
                <id>cpd</id>
                <phase>verify</phase>
                <goals>
                    <goal>cpd-check</goal>
                </goals>
            </execution>
        </executions>
     </plugin>
      ...
    </plugins>
  </build>
</project>

It uses the ruleset config/pmd/pmdMain.xml for the main code without tests. This is configured directly at the plugin level. The ruleset config/pmd/pmdTest.xml is used for the test code only. This is configured in the execution with id pmd-test.

This solution has one downside though: PMD is run three times: Twice for the main code, and once for the test code. The reason is that "pmd:check" triggers automatically "pmd:pmd", but it uses only the standard configuration (e.g. it ignores the lifecycle/execution id).

The execution pmd-test calls once "pmd:pmd" for the test code (which creates target/pmdTest/pmd.xml), then calls "pmd:check" - which itself calls "pmd:pmd" and uses the default configuration - and finally runs "pmd:check" actually, which uses the execution configuration and uses target/pmdTest/pmd.xml to decide whether to fail the build.