Gist for my spock blog post: http://www.jameselsey.co.uk/blogs/techblog/why-all-java-devs-should-at-least-consider-groovy-and-spock-for-testing Place source files in src/main and run `gradle idea` to create an intelliJ project file

build.gradle

apply plugin: 'groovy'
apply plugin: 'idea'

repositories {
    mavenCentral()
}

dependencies {
    groovy "org.codehaus.groovy:groovy-all:1.8.6"
  	testCompile "org.spockframework:spock-core:0.6-groovy-1.8" 
}

User.java

package com.jameselsey.demo.spocktutorial.domain;

public class User {

    private int id;
    private String name;
    private int age;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

UserDao.java

package com.jameselsey.demo.spocktutorial.dao;

import com.jameselsey.demo.spocktutorial.domain.User;

public interface UserDao {

    public User get(int id);
    public User findByName(String name);
    public void createUser(User user);

}

UserService.java

package com.jameselsey.demo.spocktutorial.service;

import com.jameselsey.demo.spocktutorial.dao.UserDao;
import com.jameselsey.demo.spocktutorial.domain.User;

public class UserService {

    private UserDao userDao;

    public UserService(UserDao userDao) {
        this.userDao = userDao;
    }

    public User findUser(int id){
        return userDao.get(id);
    }

    public void createUser(User user){
        User existing = userDao.findByName(user.getName());

        if(existing == null){
            userDao.createUser(user);
        } else{
            throw new RuntimeException(String.format("User with name %s already exists!", user.getName()));
        }
    }
}

UserServiceTest.groovy

package com.jameselsey.demo.spocktutorial.service

import com.jameselsey.demo.spocktutorial.dao.UserDao
import com.jameselsey.demo.spocktutorial.domain.User
import spock.lang.Specification

class UserServiceTest extends Specification {

    UserService service
    UserDao dao = Mock(UserDao)

    def setup(){
        service = new UserService(dao)
    }

    def "it gets a user by id"(){
        given:
        def id = 1

        when:
        def result = service.findUser(id)

        then:
        1 * dao.get(id) >> new User(id:id, name:"James", age:27)
        result.id == 1
        result.name == "James"
        result.age == 27
    }

    def "it saves a new user"(){
        given:
        def user = new User(id: 1, name: 'James', age:27)

        when:
        service.createUser(user)

        then:
        1 * dao.findByName(user.name) >> null

        then:
        1 * dao.createUser(user)
    }

    def "it fails to create a user because one already exists with that name"(){
        given:
        def user = new User(id: 1, name: 'James', age:27)

        when:
        service.createUser(user)

        then:
        1 * dao.findByName(user.name) >> user

        then:
        0 * dao.createUser(user)

        then:
        def exception = thrown(RuntimeException)
        exception.message == "User with name ${user.name} already exists!"
    }
}