StringSum

String Sum Kata

• Write a simple String Sum utility with a function string Sum(string num1, string num2), which can accept only natural numbers and will return their sum. Replace entered number with 0 (zero) if entered number is not a natural number.
• Stat with a simplest test case with an empty string
• Create a simple method string Sum(string num1, string num2)
• Write a test to pass small numbers and refactor, if test passed
• try to write more code and refactor