Testing persistence methods - JUnit

Question

I am writing unit tests for my project, but facing some difficulties when calling methods, which work with database. Currently I want to check a method that gets the list of publications that are of users interest, but I am getting NullPointerException :

public class TestPubManager {
    private PubManager pFunc;

    @Before
    public void initialize() {
        EntityManager manager = PersistenceManager.INSTANCE.getEntityManager();
        em.getTransaction().begin();
        PubManager pManager = new PubManager(manager);
       }

    @Test
    public void testGetInterestPubs() {
        int res = pManager.getInterestPubs(2).size();
        assertEquals(20, res);
    }
}

NullPointerException is on the line with int res = pManager.getInterestPubs(2).size(); . What am I doing wrong way?

Answer 1

I have found a solution. So the issue was in the constructor - it was not initializing in @Before annotation, but when I put it inside the test, everything worked out fine.

public class TestPubManager {
    private PubManager pFunc;
    EntityManager manager = PersistenceManager.INSTANCE.getEntityManager();

    @Before
    public void initialize() {
        em.getTransaction().begin();
       }

    @Test
    public void testGetInterestPubs() {
        PubManager pManager = new PubManager(manager);
        int res = pManager.getInterestPubs(2).size();
        assertEquals(20, res);
    }
}