Hibernate cannot get persisted object while running in test environment

DAO successfully adds new Team to database. Then I try to get persisted object back but teamDAO returns null therefore assertion throws error.

@Test
    public void addTeamTest(){
        Team team = new Team();
        team.setId(100);
        team.setName("Test team");
        team.setRating(100);
        team.setOrganization(organizationDAO.getOrganization(1));
        Set<TeamMember> teamMembers = new HashSet<TeamMember>();
        teamMembers.add(teamMemberDAO.getTeamMember(1));
        team.setTeamMembers(teamMembers);
        teamDAO.addTeam(team); // persisted to database just fine
        Team persistedTeam = teamDAO.getTeam(100);
        assertEquals(persistedTeam.getId(), 100); // persistedTeam is null. why?

    }

Why DAO or Hibernate fails to get persisted object back?