@Test
public void testNextItemId() {

    OnapPDPGroup groupNotInList = Mockito.mock(OnapPDPGroup.class);
    Object retObj = null;
    container.groups.add(group);
    container.groups.add(newGroup);
    assertNull(container.nextItemId(groupNotInList));
    assertNull(container.nextItemId(newGroup));
    retObj = container.nextItemId(group);
    assertNotNull(retObj);
    assertTrue(retObj instanceof OnapPDPGroup);
}