title: Unit test for the 'none' type in Python
body: <p>How would I go about testing for a function that does not return anything?</p>
  <p>For example, say I have this function:</p>
  <pre><code>def is_in(char):
      my_list = []
      my_list.append(char)
  </code></pre>
  <p>and then if I were to test it:</p>
  <pre><code>class TestIsIn(unittest.TestCase):
  
      def test_one(self):
      ''' Test if one character was added to the list'''
      self.assertEqual(self.is_in('a'), # And this is where I am lost)
  </code></pre>
  <p>I don't know what to assert the function is equal to, since there isn't any return value that I could compare it to.</p>
  <p>Would <em>assertIn</em> work?</p>