I was facing the same problem that the tests were not running.
<plugin>
<groupId>org.codehaus.gmavenplus</groupId>
<artifactId>gmavenplus-plugin</artifactId>
<version>1.6</version>
<executions>
<execution>
<goals>
<goal>addSources</goal>
<goal>addTestSources</goal>
<goal>compile</goal>
<goal>compileTests</goal>
</goals>
</execution>
</executions>
<configuration>
<sources>
<source>
<directory>${project.basedir}/src</directory>
<includes>
<include>**/*.groovy</include>
</includes>
</source>
<source>
<directory>${project.basedir}/vars</directory>
<includes>
<include>**/*.groovy</include>
</includes>
</source>
</sources>
<testSources>
<testSource>
<directory>${project.basedir}/src/test/groovy</directory>
<includes>
<include>*.groovy</include>
</includes>
</testSource>
</testSources>
</configuration>
</plugin>
I am using gmavenplus plugin to run those tests and I had to also add this dependency
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-all</artifactId>
<version>2.4.11</version>
<scope>test</scope>
</dependency>
After adding the two above, I could run the tests.
HTH