So I want to do this code Kata for practice. I want to implement the kata with tdd in separate files:

The algorithm:

# stringcalculator.py  
def Add(string):return 1

and the tests:

# stringcalculator.spec.py 
from stringcalculator import Add
import unittestclass TestStringCalculator(unittest.TestCase):def add_returns_zero_for_emptyString(self):self.assertEqual(Add(' '), 0)if __name__ == '__main__':unittest.main()

When running the testfile, I get:

Ran 0 tests in 0.000sOK

It should return one failed test however. What do I miss here?

As stated in the python unittest doc:

The simplest TestCase subclass will simply implement a test method(i.e. a method whose name starts with test)

So you will need to change your method name to something like this:

def test_add_returns_zero_for_emptyString(self):self.assertEqual(Add(' '), 0)