src/site/apt/examples/differentRulesetForTests.apt.vm

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 Using a different ruleset for tests
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 Andreas Dangel
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 2021-07-09
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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
 {{{https://maven.apache.org/guides/mini/guide-configuring-plugins.html#Using_the_executions_Tag}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>${project.version}</version>
        <configuration>
            <includeTests>false</includeTests>
            <rulesets>
                <ruleset>config/pmd/pmdMain.xml</ruleset>
            </rulesets>
            <linkXRef>false</linkXRef>
        </configuration>
        <executions>
            <execution>
                <id>pmd-main</id>
                <phase>verify</phase>
                <goals>
                    <goal>check</goal>
                </goals>
            </execution>
            <execution>
                <id>pmd-test</id>
                <phase>verify</phase>
                <goals>
                    <goal>pmd</goal>
                    <goal>check</goal>
                </goals>
                <configuration>
                    <targetDirectory>\${project.build.directory}/pmdTest/</targetDirectory>
                    <includeTests>true</includeTests>
                    <excludeRoots>
                        <excludeRoot>${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.