}
      iterator.forEachRemaining(targetElements::add);
      if (knownOrder == KnownOrder.KNOWN_ORDER) {
        assertEquals(expectedElements, targetElements);
      } else {
        Helpers.assertEqualIgnoringOrder(expectedElements, targetElements);
      }
    }
  }

  private void recurse(int level) {
    // We're going to reuse the stimuli array 3^steps times by overwriting it