public void NumLiveNeighborsTest()
        {
            World world = new World();
            world.AddCell(0, 0);
            world.AddCell(0, 1);
            world.AddCell(2, 3);
            world.AddCell(-1, -1);

            Assert.AreEqual(1, world.NumLiveNeighbors(0, 1));
            Assert.AreEqual(2, world.NumLiveNeighbors(0, 0));
        }