svoid test_compareTreeSetSizes() {
  LS data = uniquifyAndSort(repF(1000, -> randomID(6)));
  print("Entries: " + n2(data));
  
  L<Set<S>> sets = ll(
    new TreeSet(data),
    new CompactTreeSet(data),
    new UltraCompactTreeSet(data),
    new MegaCompactTreeSet(data));
    
  for (set : sets) {
    assertEquals(toList(set), data);
    print(className(set) + " OK, bytes per entry: " + formatDoubleRatio(guessObjectSize(set), l(data), 2));
  }
}