@Test
public void testPrevItemId() {

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