Using Python with a Test Driven approach, create a simple String Calculator which covers the following requirements:
- Adds numbers present in the input, e.g "1,2" = 3, "10,4" = 14
- Treats empty or null input as zero, e.g "" = 0, null = 0
- Supports different delimiters, e.g "1,2,3", "1 2 3"
- Does not support negative numbers
- Ignores numbers greater than 100
python coding_task
python -m pytest