从junit调用EJB方法时获取空指针异常

Question

我正在为实体java bean编写单元Junit测试用例。但是，当我调用EJB方法时，我得到一个空指针异常，代码如下所示

UserServiceTest.java

@PersistenceContext(unitName = "PU")
    private EntityManager em;    

    private static UserService userService;


    @Test
    public void registerUser() {
        userService = new UserService();
        resultData = userService.registerUser(name, email, password, mobileNumber, countryId);
        Assert.assertEquals(true, resultData.isSet);
        Assert.assertEquals(message, resultData.message);

    }

UserService.java

@PersistenceContext(unitName = "PU")
    private EntityManager em;
public ResultData registerUser(String name, String email, String password, String mobileNumber, String countryId) {    

        try {   

            Query q = em.createNamedQuery("User.findByEmail", User.class).setParameter("email", email);
            users = q.getResultList();
            if (!users.isEmpty()) {
                userDataClass.isSet = false;
                userDataClass.message = "A user with this email already exists.";

                return userDataClass;
            }catch (Exception e) {
            userDataClass.isSet = false;

        }

我调试了上面的代码。当ponter来到entityManager

时

Query q = em.createNamedQuery("User.findByEmail", User.class).setParameter("email", email);

我收到空指针异常。

任何人都可以帮助我吗