@Test
public void testGetChildrenOfSet() {

  // the child of both id2 and id3 is id1
  Set<TermId> queryTerms = ImmutableSet.of(id2, id3);
  Set<TermId> expected = ImmutableSet.of(id1, id2, id3);
  assertEquals(expected, getChildTerms(ontology, queryTerms));
}