public void TestItemsToString3()
        {
            var sequence = new[] { 1, 2, 3 };

            var result = sequence.ItemsToString("x");

            Assert.AreEqual("1x2x3", result);
        }
        public void TestItemsToString1()
        {
            var sequence = new[] { 1, 2, 3 };

            var result = sequence.ItemsToString(i => "" + i, "?");

            Assert.AreEqual("1?2?3", result);
        }