@Test
public void testUniqueItems() throws IOException {

    Path sampleFile = newGenericSample();
    try (Indexer indexer = new GenericIndexer(sampleFile, FileWorkspaceImpl.getRootFolder(sampleFile))) {
        assertThatThrownBy(() -> indexer.checkId(new Index.Key(UTIL_CAL, "Calendars2"))).isInstanceOf(IOException.class);
    }
}