@Test
public void testSubclass() {

    int maxLength = Integer.MAX_VALUE;
    IntPredicate filter = i -> true;
    
    List<Tuple2id> result0 = recommender.getRecommendation(0, maxLength, filter).getIidxs();
    assertEquals(recs, result0);
    List<Tuple2id> result1 = recommender.getRecommendation(1, maxLength, filter).getIidxs();
    assertEquals(emptyList(), result1);
}