@Test
public void testGetParentsId2() {

  // the only ancestor of id2 is id5: id2->id5
  Set<TermId> expected = ImmutableSet.of(id2, id5);
  assertEquals(expected, getParentTerms(ontology, id2));
  // id2 is not an ancestor of id5
  assertNotEquals(expected, getParentTerms(ontology, id5));
  // instead, only id5 is an ancestor of id5
  expected = ImmutableSet.of(id5);
  assertEquals(expected, getParentTerms(ontology, id5));
}