Introduce more complicated NPE analysis for Spring applications

[EgorkaKulikov]

Description

Let's generate tests for the following code snippet

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

    @Transactional
    @Override
    public void add(User user) {
        userDao.add(user);
    }

The following test is generated

@Test
  public void testListUsers_UserDaoListUsers_1() {
      /* This test fails because method [web.service.UserServiceImpl.listUsers] produces [java.lang.NullPointerException]
          web.service.UserServiceImpl.listUsers(UserServiceImpl.java:28) */
      userServiceImpl.listUsers();
  }

Actually, this test passes :)
And this behavior is correct because NPE is impossible on objects injected with Mock and InjectMocks.

Expected behavior

NPE tests should be generated only when this exception is really possible. We need to tune Symbolic engine for that.