Performance enhancements for unit tests

in test_contentstore, don't load the xml course if not necessary

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

 """
  Test contentstore.mongo functionality
 """
-import os
 import logging
 from uuid import uuid4
 import unittest

common/lib/xmodule/xmodule/poll_module.py

@@ -30,7 +30,7 @@ class PollFields(object):
 
     voted = Boolean(help="Whether this student has voted on the poll", scope=Scope.user_state, default=False)
     poll_answer = String(help="Student answer", scope=Scope.user_state, default='')
-    poll_answers = Dict(help="All possible answers for the poll fro other students", scope=Scope.user_state_summary)
+    poll_answers = Dict(help="Poll answers from all students", scope=Scope.user_state_summary)
 
     # List of answers, in the form {'id': 'some id', 'text': 'the answer text'}
     answers = List(help="Poll answers from xml", scope=Scope.content, default=[])

common/lib/xmodule/xmodule/tests/test_export.py

@@ -230,12 +230,55 @@ class ConvertExportFormat(unittest.TestCase):
 
         # Expand all the test archives and store their paths.
         self.data_dir = path(__file__).realpath().parent / 'data'
-        self.version0_nodrafts = self._expand_archive('Version0_nodrafts.tar.gz')
-        self.version1_nodrafts = self._expand_archive('Version1_nodrafts.tar.gz')
-        self.version0_drafts = self._expand_archive('Version0_drafts.tar.gz')
-        self.version1_drafts = self._expand_archive('Version1_drafts.tar.gz')
-        self.version1_drafts_extra_branch = self._expand_archive('Version1_drafts_extra_branch.tar.gz')
-        self.no_version = self._expand_archive('NoVersionNumber.tar.gz')
+
+        self._version0_nodrafts = None
+        self._version1_nodrafts = None
+        self._version0_drafts = None
+        self._version1_drafts = None
+        self._version1_drafts_extra_branch = None
+        self._no_version = None
+
+    @property
+    def version0_nodrafts(self):
+        "lazily expand this"
+        if self._version0_nodrafts is None:
+            self._version0_nodrafts = self._expand_archive('Version0_nodrafts.tar.gz')
+        return self._version0_nodrafts
+
+    @property
+    def version1_nodrafts(self):
+        "lazily expand this"
+        if self._version1_nodrafts is None:
+            self._version1_nodrafts = self._expand_archive('Version1_nodrafts.tar.gz')
+        return self._version1_nodrafts
+
+    @property
+    def version0_drafts(self):
+        "lazily expand this"
+        if self._version0_drafts is None:
+            self._version0_drafts = self._expand_archive('Version0_drafts.tar.gz')
+        return self._version0_drafts
+
+    @property
+    def version1_drafts(self):
+        "lazily expand this"
+        if self._version1_drafts is None:
+            self._version1_drafts = self._expand_archive('Version1_drafts.tar.gz')
+        return self._version1_drafts
+
+    @property
+    def version1_drafts_extra_branch(self):
+        "lazily expand this"
+        if self._version1_drafts_extra_branch is None:
+            self._version1_drafts_extra_branch = self._expand_archive('Version1_drafts_extra_branch.tar.gz')
+        return self._version1_drafts_extra_branch
+
+    @property
+    def no_version(self):
+        "lazily expand this"
+        if self._no_version is None:
+            self._no_version = self._expand_archive('NoVersionNumber.tar.gz')
+        return self._no_version
 
     def tearDown(self):
         """ Common cleanup. """