def test_update()
        # create a canvas of size 200 X 200
        Canvas.init(200, 200, "Testing_Update")
        # 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] = 0
                end
        end
	# infect one random person
	a[rand(20)][rand(20)] = 1
	display(a)
	sleep(2)
	# run the simulation for 10 "days"
	for day in 1..10 do
		a = update(a)
		display(a)
		sleep(2)
	end
end