add comment and fix mistake in test

lms/djangoapps/courseware/module_render.py

@@ -398,6 +398,8 @@ def get_module_for_descriptor_internal(user, descriptor, model_data_cache, cours
     # for studio authored courses (compared to the /course/... format) since it is
     # is durable with respect to moves and the author doesn't need to
     # know the hierarchy
+    # NOTE: module_id is empty string here. The 'module_id' will get assigned in the replacement
+    # function, we just need to specify something to get the reverse() to work
     module.get_html = replace_jump_to_id_urls(module.get_html, course_id,
                                               reverse('jump_to_id',
                                               kwargs={'course_id': course_id, 'module_id': ''}))

lms/djangoapps/courseware/tests/test_views.py

@@ -53,7 +53,7 @@ class TestJumpTo(TestCase):
 
     def test_jumpto_id_invalid_location(self):
         location = Location('i4x', 'edX', 'toy', 'NoSuchPlace', None)
-        jumpto_url = '%s/%s/jump_to/%s' % ('/courses', self.course_name, location.name)
+        jumpto_url = '%s/%s/jump_to_id/%s' % ('/courses', self.course_name, location.name)
         response = self.client.get(jumpto_url)
         self.assertEqual(response.status_code, 404)