unable to resolve class com.homeaway.devtools.jenkins.testing.JenkinsPipelineSpecification

Question

I am trying to run some spock tests with Maven. I already ran tests before with groovy version 2.4. Now when I switched to 2.5+, it shows some error.

My minimal pom is:

  <dependencies>
    <dependency>
      <groupId>org.codehaus.groovy</groupId>
      <artifactId>groovy-all</artifactId>
      <version>2.4.14</version>
      <type>pom</type>
    </dependency>

    <dependency>
      <groupId>org.spockframework</groupId>
      <artifactId>spock-core</artifactId>
      <version>2.0-groovy-2.5</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>com.homeaway.devtools.jenkins</groupId>
      <artifactId>jenkins-spock</artifactId>
      <version>2.0.0</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.8.1</version>
        <executions>
          <execution>
            <id>default-test</id>
            <goals>
              <goal>test</goal>
            </goals>
            <configuration>
              <forkCount>1</forkCount>
              <includes>
                <include>${test.pattern}</include>
              </includes>
              <useManifestOnlyJar>false</useManifestOnlyJar>
              <systemPropertyVariables>
                <root.loglevel>${test.loglevel}</root.loglevel>
                <root.appender>Stdout</root.appender>
                <test.loglevel>${test.loglevel}</test.loglevel>
                <logdir>${logdir}</logdir>
              </systemPropertyVariables>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.codehaus.gmavenplus</groupId>
        <artifactId>gmavenplus-plugin</artifactId>
        <version>1.6.1</version>
        <executions>
          <execution>
            <goals>
              <goal>addSources</goal>
              <goal>addTestSources</goal>
              <goal>compile</goal>
              <goal>compileTests</goal>
            </goals>
            <configuration>
              <sources>
                <source>
                  <directory>src</directory>
                  <includes>
                    <include>**/*.groovy</include>
                  </includes>
                </source>
              </sources>
              <testSources>
                <testSource>
                  <directory>test</directory>
                  <includes>
                    <include>**/*.groovy</include>
                  </includes>
                </testSource>
              </testSources>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

My project structure is as follows:

src
│   └── test
│       ├── vars
│       │   ├── gitCloneSpec.groovy
│       │   ├── GitRepoCloneSpec.groovy
vars
|   └── ├── gitClone.groovy
│       ├── GitRepoClone.groovy

Here is the error report: Although I already have dependency jenkins-spock in my pom, why do I get this error?

Failed to execute goal org.codehaus.gmavenplus:gmavenplus-plugin:1.6.1:compile (default) on project devops-pdk-psl: Error occurred while calling a method on a Groovy class from classpath.: InvocationTargetException: startup failed:
[ERROR] src/test/vars/gitCloneSpec.groovy: 1: unable to resolve class com.homeaway.devtools.jenkins.testing.JenkinsPipelineSpecification
[ERROR]  @ line 1, column 1.
[ERROR]    import com.homeaway.devtools.jenkins.testing.JenkinsPipelineSpecification;
[ERROR]    ^
[ERROR]
[ERROR] src/test/vars/GitRepoCloneSpec.groovy: 1: unable to resolve class com.homeaway.devtools.jenkins.testing.JenkinsPipelineSpecification
[ERROR]  @ line 1, column 1.
[ERROR]    import com.homeaway.devtools.jenkins.testing.JenkinsPipelineSpecification;
[ERROR]    ^
[ERROR]
[ERROR] 2 errors