add unit test for proper depth build out

cms/djangoapps/contentstore/tests/test_contentstore.py

@@ -307,6 +307,21 @@ class ContentStoreToyCourseTest(ModuleStoreTestCase):
         # note, we know the link it should be because that's what in the 'full' course in the test data
         self.assertContains(resp, '/c4x/edX/full/asset/handouts_schematic_tutorial.pdf')
 
+    def test_prefetch_children(self):
+        import_from_xml(modulestore(), 'common/test/data/', ['full'])
+        module_store = modulestore('direct')
+        location = CourseDescriptor.id_to_location('edX/full/6.002_Spring_2012')
+
+        course = module_store.get_item(location, depth=2)
+
+        # make sure we pre-fetched a known sequential which should be at depth=2
+        self.assertTrue(Location(['i4x', 'edX', 'full', 'sequential', 
+            'Administrivia_and_Circuit_Elements', None]) in course.system.module_data)
+
+        # make sure we don't have a specific vertical which should be at depth=3
+        self.assertFalse(Location(['i4x', 'edX', 'full', 'vertical', 'vertical_58', 
+            None]) in course.system.module_data)
+
     def test_export_course_with_unknown_metadata(self):
         module_store = modulestore('direct')
         content_store = contentstore()