diff --git a/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py b/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
index 6bebed9acc..d66e604117 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
@@ -2,6 +2,7 @@
 """
 Modulestore configuration for test cases.
 """
+import copy
 import functools
 from uuid import uuid4
 from contextlib import contextmanager
@@ -192,6 +193,8 @@ class ModuleStoreIsolationMixin(CacheIsolationMixin):
 
     MODULESTORE = mixed_store_config(mkdtemp_clean(), {})
     ENABLED_CACHES = ['mongo_metadata_inheritance', 'loc_cache']
+    __settings_overrides = []
+    __old_modulestores = []
 
     @classmethod
     def start_modulestore_isolation(cls):
@@ -201,10 +204,13 @@ class ModuleStoreIsolationMixin(CacheIsolationMixin):
         be flushed (all content will be deleted).
         """
         cls.start_cache_isolation()
-        cls.__settings_override = override_settings(
+        override = override_settings(
             MODULESTORE=cls.MODULESTORE,
         )
-        cls.__settings_override.__enter__()
+
+        cls.__old_modulestores.append(copy.deepcopy(settings.MODULESTORE))
+        override.__enter__()
+        cls.__settings_overrides.append(override)
         XMODULE_FACTORY_LOCK.enable()
         clear_existing_modulestores()
         cls.store = modulestore()
@@ -218,7 +224,9 @@ class ModuleStoreIsolationMixin(CacheIsolationMixin):
         """
         drop_mongo_collections()  # pylint: disable=no-value-for-parameter
         XMODULE_FACTORY_LOCK.disable()
-        cls.__settings_override.__exit__(None, None, None)
+        cls.__settings_overrides.pop().__exit__(None, None, None)
+
+        assert settings.MODULESTORE == cls.__old_modulestores.pop()
         cls.end_cache_isolation()
 
 
diff --git a/openedx/core/djangolib/testing/utils.py b/openedx/core/djangolib/testing/utils.py
index 4feb1749c3..5a6efbfaa0 100644
--- a/openedx/core/djangolib/testing/utils.py
+++ b/openedx/core/djangolib/testing/utils.py
@@ -1,3 +1,15 @@
+"""
+Utility classes for testing django applications.
+
+:py:class:`CacheIsolationMixin`
+    A mixin helping to write tests which are isolated from cached data.
+
+:py:class:`CacheIsolationTestCase`
+    A TestCase baseclass that has per-test isolated caches.
+"""
+
+import copy
+
 from django.core.cache import caches
 from django.test import TestCase, override_settings
 from django.conf import settings
@@ -27,7 +39,9 @@ class CacheIsolationMixin(object):
 
     CACHES = None
     ENABLED_CACHES = None
-    __settings_override = None
+
+    __settings_overrides = []
+    __old_settings = []
 
     @classmethod
     def start_cache_isolation(cls):
@@ -61,8 +75,12 @@ class CacheIsolationMixin(object):
         if cache_settings is None:
             return
 
-        cls.__settings_override = override_settings(CACHES=cache_settings)
-        cls.__settings_override.__enter__()
+        cls.__old_settings.append(copy.deepcopy(settings.CACHES))
+        override = override_settings(CACHES=cache_settings)
+        override.__enter__()
+        cls.__settings_overrides.append(override)
+
+        assert settings.CACHES == cache_settings
 
         # Start with empty caches
         cls.clear_caches()
@@ -76,9 +94,9 @@ class CacheIsolationMixin(object):
         # Make sure that cache contents don't leak out after the isolation is ended
         cls.clear_caches()
 
-        if cls.__settings_override is not None:
-            cls.__settings_override.__exit__(None, None, None)
-            cls.__settings_override = None
+        if cls.__settings_overrides:
+            cls.__settings_overrides.pop().__exit__(None, None, None)
+            assert settings.CACHES == cls.__old_settings.pop()
 
     @classmethod
     def clear_caches(cls):