Each test should only test one thing and have one assert. I'd prefer not to have a test of the default, because tests shouldn't fail just because a setting has a new (also valid) default value. Testing for `True` and `False` is good enough. Maybe the content of the dict should be quickly tested in the True condition. For instance `self.assertEqual(sub.json_dict['url'], self.comment_url)`.
`
It would also be good if the submission objects are called either submission or sub. `text` indicates that the variable is a string.