public static bool CheckDigitIsCorrect(string isbn)
        {
            if (IsbnFormat.CorrectFormat(isbn) == false || StringHandling.IsValidInput(isbn) == false)
            {
                return(false);
            }

            isbn = StringHandling.RemoveWhiteSpaceAndDashes(isbn);

            if (IsbnFormat.ContainsNumbers(isbn) == false)
            {
                return(false);
            }

            List <int> isbnList   = StringHandling.IsbnStringToList(isbn);
            int        checkDigit = CheckDigit(isbnList);

            if (checkDigit == isbnList[12])
            {
                return(true);
            }
            else
            {
                return(false);
            }
        }
        public void removed_extra_characters()
        {
            string input = "a b c";

            string inputRemoved = StringHandling.RemoveWhiteSpaceAndDashes(input);

            Assert.AreEqual("abc", inputRemoved);
        }
        public void string_is_converted_to_list()
        {
            List <int> listOfNum = new List <int>();

            listOfNum.Add(1);
            listOfNum.Add(2);
            listOfNum.Add(3);

            List <int> functionList = StringHandling.IsbnStringToList("123");

            Assert.AreEqual(listOfNum, functionList);
        }
        public void is_valid_string_input()
        {
            bool validInput = StringHandling.IsValidInput("aa");

            Assert.AreEqual(true, validInput);
        }