new_contents: from django.test import TestCase
  
  from ..forms import BasePersonForm
  
  class TestValidators(TestCase):
  
      def test_twitter_bad_url(self):
          form = BasePersonForm({
              'name': 'John Doe',
              'twitter_username': 'http://example.org/blah',
          })
          self.assertFalse(form.is_valid())
          self.assertEqual(
              form.errors,
              {
                  'twitter_username':
                  [u'The Twitter username must only consist of alphanumeric characters or underscore']
              }
          )
  
      def test_twitter_fine(self):
          form = BasePersonForm({
              'name': 'John Doe',
              'twitter_username': 'madeuptwitteraccount',
          })
          self.assertTrue(form.is_valid())
          self.assertEqual(form.errors, {})
          self.assertEqual(
              form.cleaned_data['twitter_username'],
              'madeuptwitteraccount'
          )
  
      def test_twitter_full_url(self):
          form = BasePersonForm({
              'name': 'John Doe',
              'twitter_username': 'https://twitter.com/madeuptwitteraccount',
          })
          self.assertTrue(form.is_valid())
          self.assertEqual(form.errors, {})
          self.assertEqual(
              form.cleaned_data['twitter_username'],
              'madeuptwitteraccount'
          )
          
  
subject: Add tests for the twitter_username validator