// Testing: make sure the number of nodes in the tree is the same as the amount put in:
 public void sanityCheckNumNodes() {
   int sanity = viewedPos.sanityCheckGetNumberOfNodes();
   if (sanity != numPosRecorded) {
     System.err.println(
         "ERROR: the number of nodes in the tree is not equal to the number of nodes added. #Added: "
             + numPosRecorded
             + " number received: "
             + sanity);
     System.exit(1);
   }
 }