@Override
  public Set<String> getUuids() {
    checkState(uuids != null, "UUIDs have not been set in repository");
    return uuids;
  }
@Test
  public void getUuids_fails_if_not_initialized() {
    assertThatThrownBy(() -> underTest.getUuids())
      .isInstanceOf(IllegalStateException.class)
      .hasMessage("UUIDs have not been set in repository");
  }