plugin.xml

<plugin>
  <groupId>org.codehaus.groovy.maven</groupId>
  <artifactId>gmaven-plugin</artifactId>
  <version>1.0-rc-3</version>
  <extensions>true</extensions>
  <executions>
    <execution>
      <goals>
        <goal>testCompile</goal>
      </goals>
      <configuration>
        <sources>
          <fileset>
            <directory>${pom.basedir}/src/test/java</directory>
            <includes>
              <include>**/*.groovy</include>
            </includes>
          </fileset>
        </sources>
      </configuration>
    </execution>
  </executions>
</plugin>