@Test
void testBuilderNoRoot() {

  TermId childId = TermId.of("HP:0000001");
  Term child = Term.of(childId, "child");
  TermId child2Id = TermId.of("HP:0000002");
  Term child2 = Term.of(child2Id, "child2");
  assertThrows(PhenolRuntimeException.class, () -> ImmutableOntology.builder()
    .terms(ImmutableList.of(child, child2))
    .relationships(ImmutableList.of())
    .build(), "No root candidate found.");
}