public void TestExample()
        {
            var expected = new int[, ]
            {
                { 1, 4, 3 },
                { 1, 4, 4 },
                { 2, 3, 4 }
            };

            var actual = new int[, ]
            {
                { 1, 2, 3 },
                { 1, 2, 2 },
                { 2, 3, 2 }
            };

            CollectionAssert.AreEqual(expected, Kata.FloodFill(actual, 0, 1, 4));
        }