Basic tests of N() node trees representation:

1 


  1  
+---+
2   3 


  1  
+---+
    2 


  1  
+---+
2     


      1      
  +-------+  
  2       3  
+---+   +---+
4   5       6 


   abcdef   
  +-------+ 
hello   ugly 


            hello            
      +---------------+      
      1               1      
  +-------+       +-------+  
  2       3       2       3  
+---+   +---+   +---+   +---+
4   5       6   4   5       6 


 abcdefg  
+--------+
1        2 


     1            
+----------+      
2   abcdefghilmnop 


          0123456789           
     +-------------------+     
     1                abcdefg  
+----------+         +--------+
2   abcdefghilmnop   1        2 


                         hellllllllo                         
              +-------------------------------+              
            hello                           hello            
      +---------------+               +---------------+      
      1               1               1               1      
  +-------+       +-------+       +-------+       +-------+  
  2       3       2       3       2       3       2       3  
+---+   +---+   +---+   +---+   +---+   +---+   +---+   +---+
4   5       6   4   5       6   4   5       6   4   5       6 


Mixed tests with trees represented with N() nodes:
Complete binary tree depth: 7
                                                                              X                                                                                
                                      +-------------------------------------------------------------------------------+                                        
                                      X                                                                               X                                        
                  +---------------------------------------+                                       +---------------------------------------+                    
                  X                                       X                                       X                                       X                    
        +-------------------+                   +-------------------+                   +-------------------+                   +-------------------+          
        X                   X                   X                   X                   X                   X                   X                   X          
   +---------+         +---------+         +---------+         +---------+         +---------+         +---------+         +---------+         +---------+     
   X         X         X         X         X         X         X         X         X         X         X         X         X         X         X         X     
 +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+    +----+  
 X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X    X  
+--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+ +--+
X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X X  X