[StringCalc0506] First test case with empty or nil string
[StringCalc0506] Add class StringCalc with function Calc
[StringCalc0506] after red, change return 0 to green
[StringCalc0506] refactor
[StringCalc0506] Red - string contains 1 number
[StringCalc0506] green
[StringCalc0506] refactor
[StringCalc0506] new test with string contains more than 1 numbers
[StringCalc0506] Green
[StringCalc0506] refactor
[StringCalc0506] RED
[StringCalc0506] Green
[StringCalc0506] refactor
Out of time