@Override
	public boolean runTest(){
		return (diff21(19) == 2 &&
				diff21(10) == 11 &&
				diff21(21) == 0 &&
				diff21(22) == 2 &&
				diff21(25) == 8 &&
				diff21(30) == 18 &&
				diff21(0) == 21 &&
				diff21(1) == 20 &&
				diff21(2) == 19 &
				diff21(-1) == 22 &
				diff21(-2) == 23 &
				diff21(50) == 58);
	}