java.lang.NullPointerException
at service.KweetServices.createUser(KweetServices.java:35)
at service.KweetServices$createUser$1.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
at KweetServicesTest.testCreateUser(KweetServicesTest.groovy:58)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at junit.framework.TestCase.runTest(TestCase.java:176)
at junit.framework.TestCase.runBare(TestCase.java:141)
at junit.framework.TestResult$1.protect(TestResult.java:122)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at junit.framework.TestResult.run(TestResult.java:125)
at junit.framework.TestCase.run(TestCase.java:129)
at junit.framework.TestSuite.runTest(TestSuite.java:252)
at junit.framework.TestSuite.run(TestSuite.java:247)
at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:86)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

public interface UserDAO {

    int count();

    boolean create(User user);

    boolean edit(User user);

    List<User> findAll();

    User findUserByUsername(String username);

    boolean remove(User user);

}

package dao;

import domain.User;

import javax.ejb.Stateless;
import javax.persistence.PersistenceContext;
import javax.persistence.EntityManager;
import java.util.List;

/**
 * Created by Nick on 08-Mar-17.
 */
@Stateless
public class UserDAOJPAImpl implements UserDAO{
    @PersistenceContext
    private EntityManager em;

    public UserDAOJPAImpl() {
    }


    @Override
    public int count() {
        int i = (Integer) em.createNamedQuery("countUsers").getSingleResult();
        return i;
    }

    @Override
    public boolean create(User user) {
        User toCreate = findUserByUsername(user.getUserName());
        if(toCreate == null)
        {
            em.persist(user);
            return true;
        }
        return false;
    }

    @Override
    public boolean edit(User user) {
        User toEdit = findUserByUsername(user.getUserName());
        if(toEdit == null)
        {
            em.merge(user);
            return true;
        }
        return false;
    }

    @Override
    public List<User> findAll() {
        return (List<User>) em.createNamedQuery("findAllUsers", User.class).getResultList();
    }

    @Override
    public User findUserByUsername(String username) {
        return em.find(User.class, username);
    }

    @Override
    public boolean remove(User user) {
        User userToRemove = findUserByUsername(user.getUserName());
        if(userToRemove != null)
        {
            em.remove(user);
            return true;
        }
        return false;

    }



}

@Entity
@NamedQueries({
        @NamedQuery(name = "findAllUsers", query = "select u from User u"),
        @NamedQuery(name = "countUsers", query = "select count(u) from User u")
})
public class User implements Serializable{

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

    private String name;

    private String userName;

    private String password;

    private String role;



    private String eMail;
    private String bio;
    private String location;
    private String avatar;

    public User(String name, String userName, String password, String role, String eMail, String bio, String location, String avatar, String webPage) {
        this.name = name;
        this.userName = userName;
        this.password = password;
        this.role = role;
        this.eMail = eMail;
        this.bio = bio;
        this.location = location;
        this.avatar = avatar;
        this.webPage = webPage;
    }

    private String webPage;

    @ManyToMany
    private Collection<User> followers = new ArrayList();
    @ManyToMany
    private Collection<User> following = new ArrayList();

    @OneToMany
    private Collection<Kweet> kweets = new ArrayList();

    public User(){

    }

    public User(String userName, String password, String role){
    this.userName = userName;
    this.password = password;
    this.role = role;
    }



    public void addKweet(Kweet kweet) {
        this.kweets.add(kweet);
    }

    public void removeKweet(Kweet kweet) {
        Iterator<Kweet> iter = kweets.iterator();
        while (iter.hasNext()) {
            Kweet kwt = iter.next();
            if (kwt.getOwner().equals(kweet.getOwner())) {
                if (kwt.getMessage().equals(kweet.getMessage())) {
                    iter.remove();
                }
            }
        }
    }



    //<editor-fold defaultstate="collapsed"
    public int getId() {
        return id;
    }

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

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }

    public Collection<User> getFollowers() {
        return followers;
    }

    public void setFollowers(Collection<User> followers) {
        this.followers = followers;
    }

    public Collection<User> getFollowing() {
        return following;
    }

    public void setFollowing(Collection<User> following) {
        this.following = following;
    }

    public Collection<Kweet> getKweets() {
        return kweets;
    }

    public void setKweets(Collection<Kweet> kweets) {
        this.kweets = kweets;
    }

    public String geteMail() {
        return eMail;
    }

    public void seteMail(String eMail) {
        this.eMail = eMail;
    }

    public String getBio() {
        return bio;
    }

    public void setBio(String bio) {
        this.bio = bio;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

    public String getAvatar() {
        return avatar;
    }

    public void setAvatar(String avatar) {
        this.avatar = avatar;
    }

    public String getWebPage() {
        return webPage;
    }

    public void setWebPage(String webPage) {
        this.webPage = webPage;
    }
    //</editor-fold>

}

@Stateless
public class KweetServices implements Serializable {


    @Inject
    private UserDAO userDAO;

    @Inject
    private KweetDAO kweetDAO;

    public void removeKweet(Kweet kweet) {
        kweetDAO.removeKweet(kweet);
    }
    public Kweet findKweet(Kweet kweet) {return kweetDAO.findKweet(kweet);}
    public boolean createKweet(Kweet kweet){return kweetDAO.createKweet(kweet);}
    public Collection<Kweet> getMentioned(Long id) {
        return kweetDAO.getMentioned(id);
    }
    public boolean createUser(User user){return userDAO.create(user);}



    public UserDAO getUserDAO() {
        return userDAO;
    }

    public void setUserDAO(UserDAO userDAO) {
        this.userDAO = userDAO;
    }

    public KweetDAO getKweetDAO() {
        return kweetDAO;
    }

    public void setKweetDAO(KweetDAO kweetDAO) {
        this.kweetDAO = kweetDAO;
    }


}

class KweetServicesTest extends GroovyTestCase {

    KweetServices service;

    @Mock
    UserDAO userdao;

    @Mock
    KweetDAO kweetdao;

    User user1;
    User user2;

    Kweet tweet1;
    Kweet tweet2;

    void setUp() {
        super.setUp()
        service = new KweetServices();
        service.setUserDAO(userdao);
        service.setKweetDAO(kweetdao);

        user1 = new User("hai","user1", "password1", "admin","nick@bijmoer.nl","hoi","breda","ja","nee");
        user2 = new User("hai2","user12", "password12", "admin2","nick@bijmoer.nl2","hoi2","breda2","ja2","nee2");


        tweet1 = new Kweet("tweet 1", new Date(), user1);
        tweet2 = new Kweet("tweet 2", new Date(), user2);

    }


    void tearDown() {

    }

    void testCreateUser() {
    service.createUser(user1);
        verify(userdao, Mockito.times(1)).create(user1);
    }


}