public void Writing_pixels_to_a_canvas()
        {
            var canvas = new MutableCanvas(10, 20);

            canvas.SetPixel(2, 3, Colors.Red);
            canvas.GetPixel(2, 3).Should().Be(Colors.Red);
        }
        public void Creating_a_canvas()
        {
            var canvas = new MutableCanvas(10, 20);

            canvas.Width.Should().Be(10);
            canvas.Height.Should().Be(20);

            for (int y = 0; y < 20; y++)
            {
                for (int x = 0; x < 10; x++)
                {
                    canvas.GetPixel(x, y).Should().Be(Colors.Black);
                }
            }
        }