@Test
public void testUniqueItems() throws IOException {

    Path sampleFile = newLegacySample();
    try (Indexer indexer = new LegacyIndexer(sampleFile)) {
        assertThatThrownBy(() -> indexer.checkId(new Index.Key(UTIL_CAL, "Calendars2"))).isInstanceOf(IOException.class);
        assertThatThrownBy(() -> indexer.checkId(new Index.Key(UTIL_VAR, "Variables2"))).isInstanceOf(IOException.class);
    }
}