def test_edit_post_errors(self):
        p = PostFactory()
        t = p.thread
        u = p.author

        self.client.login(username=u.username, password='testpass')
        response = post(self.client, 'forums.edit_post',
                        {'content': 'wha?'}, args=[t.forum.slug, t.id, p.id])

        doc = pq(response.content)
        errors = doc('ul.errorlist li a')
        eq_(errors[0].text,
            'Your message is too short (4 characters). ' +
            'It must be at least 5 characters.')
Changing post content works.
dataset/ETHPy150Open mozilla/kitsune/kitsune/forums/tests/test_templates.py/PostsTemplateTests.test_edit_post_errors