pom.xml

<?xml version="1.0"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>net.glamenv-septzen</groupId>
  <artifactId>maven3-junit-spock-testng-mixin</artifactId>
  <version>1.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>spock, TestNG, Maven3 Integration Demo</name>

  <!-- from https://github.com/spockframework/spock-example/blob/master/pom.xml -->

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version.source>1.8</java.version.source>
    <java.version.target>1.8</java.version.target>
    <surefire.version>2.19.1</surefire.version>
  </properties>

  <build>
    <plugins>
      <plugin>
        <!-- see: https://github.com/groovy/groovy-eclipse/wiki/Groovy-Eclipse-Maven-plugin -->
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.5.1</version>
        <configuration>
          <compilerId>groovy-eclipse-compiler</compilerId>
          <source>${java.version.source}</source>
          <target>${java.version.target}</target>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy-eclipse-compiler</artifactId>
            <version>2.9.2-01</version>
          </dependency>
          <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy-eclipse-batch</artifactId>
            <version>2.4.3-01</version>
          </dependency>
        </dependencies>
      </plugin> 
      <plugin>
        <!--
        [ How to execute JUnit(=Spock) and TestNG test cases at same time ? ]
        see: http://solidsoft.wordpress.com/2013/03/12/mixing-testng-and-junit-tests-in-one-maven-module-2013-edition/
        -->
        <artifactId>maven-surefire-plugin</artifactId>
        <version>${surefire.version}</version>
        <dependencies>
          <dependency>
            <groupId>org.apache.maven.surefire</groupId>
            <artifactId>surefire-junit47</artifactId>
            <version>${surefire.version}</version>
          </dependency>
          <dependency>
            <groupId>org.apache.maven.surefire</groupId>
            <artifactId>surefire-testng</artifactId>
            <version>${surefire.version}</version>
          </dependency>
        </dependencies>
        <configuration>

          <!-- resolve "Cannot use a threadCount parameter less than 1; 1 > 0" error. -->
          <threadCount>1</threadCount>

          <includes>
            <!-- for JUnit, explicitly add xxxSpec and xxxTest file patterns. -->
            <!-- (mysteriously, ".groovy" dosn't work for Spock's xxxxSpec.groovy, but ".java" work!!) -->
            <include>**/*Spec.java</include>
            <include>**/*Test.java</include>
          </includes>
        </configuration>
      </plugin>
    </plugins>
  </build>

  <dependencies>
    <dependency>
      <groupId>org.codehaus.groovy</groupId>
      <artifactId>groovy-all</artifactId>
      <version>[2.4,)</version>
    </dependency>
    <dependency>
      <groupId>org.spockframework</groupId>
      <artifactId>spock-core</artifactId>
      <version>1.0-groovy-2.4</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.testng</groupId>
      <artifactId>testng</artifactId>
      <version>[6.9,)</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

</project>