public void LabyrinthValidCellTest()
        {
            const int height    = 3;
            const int width     = 6;
            var       labyrinth = new Labyrinth(height, width);

            for (var i = 0; i < height; i++)
            {
                for (var j = 0; j < width; j++)
                {
                    Assert.IsTrue(labyrinth.IsValidCell(i, j));
                }
            }

            for (var i = 0; i < height; i++)
            {
                Assert.IsFalse(labyrinth.IsValidCell(i, -1));
                Assert.IsFalse(labyrinth.IsValidCell(i, width));
            }

            for (var j = 0; j < width; j++)
            {
                Assert.IsFalse(labyrinth.IsValidCell(-1, j));
                Assert.IsFalse(labyrinth.IsValidCell(height, j));
            }
        }