def METHOD_NAME(self):
    # use with AVATAR_ALLOWED_FILE_EXTS = ('.jpg', '.png')
    response = upload_helper(self, "imagefilewithoutext")
    self.assertEqual(response.status_code, 200)
    self.assertEqual(len(response.redirect_chain), 0) # Redirect only if it worked        
    self.assertNotEqual(response.context['upload_avatar_form'].errors, {})