def test_display()
        # create a canvas of size 200 X 200
        Canvas.init(200, 200, "Testing_Display")
        # initialize matrix a
        a = Array.new(20)
        for i in 0..19 do
                a[i] = Array.new(20)
                for j in 0..19 do
                        a[i][j] = rand(7)
                end
        end
	# display the matrix using your display function
	display(a)
end