@Override
  public void setUuids(Set<String> uuids) {
    checkState(this.uuids == null, "UUIDs have already been set in repository");
    this.uuids = uuids;
  }
@Test
  public void setUuids_fails_if_called_twice() {
    underTest.setUuids(ImmutableSet.of("U1", "U2"));

    assertThatThrownBy(() -> underTest.setUuids(ImmutableSet.of("U1", "U2")))
      .isInstanceOf(IllegalStateException.class)
      .hasMessage("UUIDs have already been set in repository");
  }