@Test
public void testGetParentsId1() {

  // id1 has three parents. Since id5 is a parent of both id2 ans id1, id1 has three ancestors (four including id1)
  //id1->id2, id1->id3, id1 -> id4; id2->id5, id3-> id5,
  // id5 is not a parent of id1, though!
  Set<TermId> expected = ImmutableSet.of(id1, id2, id3, id4);
  assertEquals(expected, getParentTerms(ontology, id1));
}