def test_display()
  n = 17
  # seed the random number generator
  srand(15110)                            
  # create a canvas of size 340 X 340
  Canvas.init(n*20, n*20, "Testing_Display")
  # initialize forest matrix randomly
  forest = Array.new(n)         # 15 rows
  for i in 0..n-1 do
    forest[i] = Array.new(n)  # create 15 columns for each row
    for j in 0..n-1 do
      forest[i][j] = rand(5) # pick a random tree state (0-4) 
    end
  end
  # display the forest using your display function
  display(forest)
end