@VisibleForTesting
  static String extractUrn(MonitoringInfoSpecs.Enum value) {
    return value.getValueDescriptor().getOptions().getExtension(monitoringInfoSpec).getUrn();
  }
@Test
  public void testUniqueUrnsDefinedForAllSpecs() {
    Multimap<String, MonitoringInfoSpecs.Enum> urnToEnum = ArrayListMultimap.create();
    for (MonitoringInfoSpecs.Enum value : MonitoringInfoSpecs.Enum.values()) {
      if (value != MonitoringInfoSpecs.Enum.UNRECOGNIZED) {
        urnToEnum.put(extractUrn(value), value);
      }
    }
    for (String urn : ImmutableSet.copyOf(urnToEnum.keySet())) {
      if (urnToEnum.get(urn).size() == 1) {
        urnToEnum.removeAll(urn);
      }
    }
    assertThat(urnToEnum.entries(), Matchers.empty());
  }