svoid test_LongTreeSet() {
  L<Long> list = repF(1000, () -> randomLong());
  Set<Long> set = asTreeSet(list);
  LongTreeSet cset = new(set);
  print(set);
  print(cset);
  assertEquals(asList(set), asList(cset));
  assertEqualsVerbose(l(set), cset.size());
  
  for (Long a : shuffledIterator(list)) {
    set.remove(a);
    cset.remove(a);
    assertEquals(asList(set), asList(cset));
    assertEqualsVerbose(l(set), cset.size());
  }
}

Began life as a copy of #1029167