public void TestMementoToReturnValidObjectState()
        {
            var grid = new Grid();
            var tile = new Tile("1", 1, TileType.Number);
            var emptyTile = new Tile(string.Empty, GlobalConstants.TotalTilesCount - 1, TileType.Empty);
            var anotherTile = new Tile("2", 2, TileType.Number);
            grid.AddTile(tile);
            grid.AddTile(emptyTile);
            Memento memento = grid.SaveMemento();

            grid.AddTile(anotherTile);
            grid.RestoreMemento(memento);

            var actual = grid.TilesCount;
            var expected = 2;
            Assert.AreEqual(expected, actual);
        }