title: Python unittest - Ran 0 tests in 0.000s
body: <p>So I want to do this code <a href="http://osherove.com/tdd-kata-1/" rel="noreferrer">Kata</a> for practice.
  I want to implement the kata with tdd in separate files:</p>
  
  <p>The algorithm:</p>
  
  <pre><code># stringcalculator.py  
  def Add(string):
     return 1
  </code></pre>
  
  <p>and the tests:</p>
  
  <pre><code># stringcalculator.spec.py 
  from stringcalculator import Add
  import unittest
  
  class TestStringCalculator(unittest.TestCase):
      def add_returns_zero_for_emptyString(self):
          self.assertEqual(Add(' '), 0)
  
  if __name__ == '__main__':
      unittest.main()
  </code></pre>
  
  <p>When running the testfile, I get:</p>
  
  <pre><code>Ran 0 tests in 0.000s
  
  OK
  </code></pre>
  
  <p>It should return one failed test however. What do I miss here?</p>