title: I keep getting an error in PyCharm, No tests were found and Empty Suite
body: <p>I keep getting an error while trying to do a test in PyCharm. It keeps saying No tests were found and empty suite. I've tried to tinker with a bunch of different things and can't seem to get this figured out. Does anyone know what the issue is?</p>
  
  <pre><code>import unittest
  from city_functions import city_country
  
  
  class TestCitiesCase(unittest.TestCase):
      """Tests the combined function in city_functions"""
  
      def test_city_country(self):
          """Does seattle united states of america work"""
          seattle = city_country('seattle', 'united states of america')
          self.assertEqual(seattle, 'seattle, united states of america')
  
      def test_city_country_population(self):
          """Does seattle united states of america population 500000 work?"""
          seattle = city_country('seattle', 'united states of america', 500000)
          self.assertEqual(seattle, 'seattle, united states of america, population 500000')
  
  
  unittest.main()
  </code></pre>
  
  <p>city_functions.py -</p>
  
  <pre><code>def city_country(city, country, population=''):
      if population:
          city = city.title() + ', ' + country.title() + ', population ' + str(population)
      else:
          city = city.title() + ', ' + country.title()
      return city
  </code></pre>