public void DecryptNumbers3()
        {
            Decryption numbers = new Decryption();

            char[] key    = "23456789012345678900987654321".ToCharArray();
            string answer = numbers.DecryptNumbers(key);

            Assert.AreEqual("12345678901234567899876543210", answer);
        }
        public void DecryptNumbers2()
        {
            Decryption numbers = new Decryption();

            char[] key    = "3579".ToCharArray();
            string answer = numbers.DecryptNumbers(key);

            Assert.AreEqual("2468", answer);
        }