Clear caches between tests for ModuleStoreTestCase/SharedModuleStoreTestCase

Cached values were leaking across tests, causing difficult to debug errors,
particularly when using Config Models. As part of this work, certain tests
that had query counts that relied on those values being cached needed to
be adjusted up.

common/djangoapps/util/tests/test_django_utils.py

@@ -0,0 +1,53 @@
+"""
+THE TESTS IN THIS MODULE SHOULD BE RUN ON THE SAME PROCESS TO BE MEANINGFUL!!!
+
+The tests in this module look kind of goofy, but the idea is to make sure that
+cache values can't leak between different TestCase classes and methods. The need
+for this will go away whenever Django merges the fix to reset the caches between
+tests (https://code.djangoproject.com/ticket/11505).
+"""
+from django.core.cache import caches
+
+from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase, SharedModuleStoreTestCase
+
+
+class CacheCheckMixin(object):
+    """Base mixin that does our cache check."""
+
+    def check_caches(self, key):
+        """Check that caches are empty, and add values."""
+        for cache in caches.all():
+            self.assertIsNone(cache.get(key))
+            cache.set(key, "Not None")
+
+
+class CacheModuleStoreTestCaseParent(ModuleStoreTestCase, CacheCheckMixin):
+    """Make sure that we're clearing cache values between tests."""
+
+    def test_cache_reset_1(self):
+        """Check to make sure cache is empty, and add values to it."""
+        self.check_caches("mstc_cache_test_key")
+
+    def test_cache_reset_2(self):
+        """Check to make sure cache is empty, and add values to it."""
+        self.check_caches("mstc_cache_test_key")
+
+
+class CacheModuleStoreTestCaseChild(CacheModuleStoreTestCaseParent):  # pylint: disable=test-inherits-tests
+    """Make sure that we're clearing cache values between classes."""
+
+
+class CacheSharedModuleStoreTestCaseParent(SharedModuleStoreTestCase, CacheCheckMixin):
+    """Make sure that we're clearing cache values between tests."""
+
+    def test_cache_reset_1(self):
+        """Check to make sure cache is empty, and add values to it."""
+        self.check_caches("smstc_cache_test_key")
+
+    def test_cache_reset_2(self):
+        """Check to make sure cache is empty, and add values to it."""
+        self.check_caches("smstc_cache_test_key")
+
+
+class CacheSharedModuleStoreTestCaseChild(CacheSharedModuleStoreTestCaseParent):  # pylint: disable=test-inherits-tests
+    """Make sure that we're clearing cache values between classes."""

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

@@ -7,6 +7,7 @@ from uuid import uuid4
 
 from mock import patch
 
+import django.core.cache
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.test import TestCase
@@ -215,6 +216,16 @@ TEST_DATA_SPLIT_MODULESTORE = mixed_store_config(
 )
 
 
+def clear_all_caches():
+    """Clear all caches so that cache info doesn't leak across test cases."""
+    # This will no longer be necessary when Django adds (in Django 1.10?):
+    #     https://code.djangoproject.com/ticket/11505
+    for cache in django.core.cache.caches.all():
+        cache.clear()
+
+    RequestCache().clear_request_cache()
+
+
 class SharedModuleStoreTestCase(TestCase):
     """
     Subclass for any test case that uses a ModuleStore that can be shared
@@ -268,7 +279,7 @@ class SharedModuleStoreTestCase(TestCase):
     @classmethod
     def tearDownClass(cls):
         drop_mongo_collections()  # pylint: disable=no-value-for-parameter
-        RequestCache().clear_request_cache()
+        clear_all_caches()
         XMODULE_FACTORY_LOCK.disable()
         cls._settings_override.__exit__(None, None, None)
 
@@ -280,6 +291,11 @@ class SharedModuleStoreTestCase(TestCase):
         OverrideFieldData.provider_classes = None
         super(SharedModuleStoreTestCase, self).setUp()
 
+    def tearDown(self):
+        """Reset caches."""
+        clear_all_caches()
+        super(SharedModuleStoreTestCase, self).tearDown()
+
     def reset(self):
         """
         Manually run tearDownClass/setUpClass again.
@@ -394,7 +410,7 @@ class ModuleStoreTestCase(TestCase):
         clear_existing_modulestores()
 
         self.addCleanup(drop_mongo_collections)
-        self.addCleanup(RequestCache().clear_request_cache)
+        self.addCleanup(clear_all_caches)
 
         # Enable XModuleFactories for the space of this test (and its setUp).
         self.addCleanup(XMODULE_FACTORY_LOCK.disable)