code: private boolean isWellFormed()
      {
          for (int i = 0 ; i < maxHeight ; i++)
          {
              int c = 0;
              for (Node node = head ; node != null ; node = node.next(i))
              {
                  if (node.prev(i) != null && node.prev(i).next(i) != node)
                      return false;
                  if (node.next(i) != null && node.next(i).prev(i) != node)
                      return false;
                  c += node.size[i];
                  if (i + 1 < maxHeight && node.parent(i + 1).next(i + 1) == node.next(i))
                  {
                      if (node.parent(i + 1).size[i + 1] != c)
                          return false;
                      c = 0;
                  }
              }
              if (i == maxHeight - 1 && c != size + 1)
                  return false;
          }
          return true;
      }
docs: don't create a separate unit test - tools tree doesn't currently warrant them