Add test for ignoring tilde files on import of extra content

common/lib/xmodule/xmodule/modulestore/tests/test_xml.py

 import os.path
+import unittest
+from glob import glob
+from mock import patch
 
 from nose.tools import assert_raises, assert_equals  # pylint: disable=E0611
 
 from xmodule.course_module import CourseDescriptor
 from xmodule.modulestore.xml import XMLModuleStore
-from xmodule.modulestore import XML_MODULESTORE_TYPE
+from xmodule.modulestore import Location, XML_MODULESTORE_TYPE
 
 from .test_modulestore import check_path_to_location
 from xmodule.tests import DATA_DIR
 
+def glob_tildes_at_end(path):
+    """
+    A wrapper for the `glob.glob` function, but it always returns
+    files that end in a tilde (~) at the end of the list of results.
+    """
+    result = glob(path)
+    with_tildes = [f for f in result if f.endswith("~")]
+    no_tildes = [f for f in result if not f.endswith("~")]
+    return no_tildes + with_tildes
 
-class TestXMLModuleStore(object):
+
+class TestXMLModuleStore(unittest.TestCase):
     def test_path_to_location(self):
         """Make sure that path_to_location works properly"""
 
@@ -42,3 +55,19 @@ class TestXMLModuleStore(object):
         location = CourseDescriptor.id_to_location("edX/toy/2012_Fall")
         errors = modulestore.get_item_errors(location)
         assert errors == []
+
+    @patch("xmodule.modulestore.xml.glob.glob", side_effect=glob_tildes_at_end)
+    def test_tilde_files_ignored(self, fake_glob):
+        modulestore = XMLModuleStore(DATA_DIR, course_dirs=['tilde'], load_error_modules=False)
+        course_module = modulestore.modules['edX/tilde/2012_Fall']
+        about_location = Location({
+            'tag': 'i4x',
+            'org': 'edX',
+            'course': 'tilde',
+            'category': 'about',
+            'name': 'index',
+        })
+        about_module = course_module[about_location]
+        self.assertIn("GREEN", about_module.data)
+        self.assertNotIn("RED", about_module.data)
+

common/test/data/tilde/about/index.html

+GREEN

common/test/data/tilde/about/index.html~

+RED

common/test/data/tilde/course.xml

+<course org="edX" course="tilde" slug="2012_Fall"/>

common/test/data/tilde/course/2012_Fall.xml

+<course>
+</course>