Removed some direct settings manipulations in tests; refs #21230.

16 files changed, 137 insertions, 223 deletions

diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index 76a5a92f4b..684259d9bf 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -56,7 +56,8 @@ ERROR_MESSAGE = "Please enter the correct username and password \
 for a staff account. Note that both fields may be case-sensitive."
 
 
-@override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
+@override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',),
+                   USE_I18N=True, USE_L10N=False, LANGUAGE_CODE='en')
 class AdminViewBasicTestCase(TestCase):
     fixtures = ['admin-views-users.xml', 'admin-views-colors.xml',
                 'admin-views-fabrics.xml', 'admin-views-books.xml']
@@ -69,16 +70,9 @@ class AdminViewBasicTestCase(TestCase):
     urls = "admin_views.urls"
 
     def setUp(self):
-        self.old_USE_I18N = settings.USE_I18N
-        self.old_USE_L10N = settings.USE_L10N
-        self.old_LANGUAGE_CODE = settings.LANGUAGE_CODE
         self.client.login(username='super', password='secret')
-        settings.USE_I18N = True
 
     def tearDown(self):
-        settings.USE_I18N = self.old_USE_I18N
-        settings.USE_L10N = self.old_USE_L10N
-        settings.LANGUAGE_CODE = self.old_LANGUAGE_CODE
         self.client.logout()
         formats.reset_format_cache()
 
@@ -2410,15 +2404,12 @@ class AdminActionsTest(TestCase):
         self.client.post('/test_admin/admin/admin_views/subscriber/', delete_confirmation_data)
         self.assertEqual(Subscriber.objects.count(), 0)
 
+    @override_settings(USE_THOUSAND_SEPARATOR=True, USE_L10N=True)
     def test_non_localized_pk(self):
         """If USE_THOUSAND_SEPARATOR is set, make sure that the ids for
         the objects selected for deletion are rendered without separators.
         Refs #14895.
         """
-        self.old_USE_THOUSAND_SEPARATOR = settings.USE_THOUSAND_SEPARATOR
-        self.old_USE_L10N = settings.USE_L10N
-        settings.USE_THOUSAND_SEPARATOR = True
-        settings.USE_L10N = True
         subscriber = Subscriber.objects.get(id=1)
         subscriber.id = 9999
         subscriber.save()
@@ -2431,8 +2422,6 @@ class AdminActionsTest(TestCase):
         self.assertTemplateUsed(response, 'admin/delete_selected_confirmation.html')
         self.assertContains(response, 'value="9999"')  # Instead of 9,999
         self.assertContains(response, 'value="2"')
-        settings.USE_THOUSAND_SEPARATOR = self.old_USE_THOUSAND_SEPARATOR
-        settings.USE_L10N = self.old_USE_L10N
 
     def test_model_admin_default_delete_action_protected(self):
         """
@@ -4127,21 +4116,16 @@ class ValidXHTMLTests(TestCase):
         self.assertNotContains(response, ' xml:lang=""')
 
 
-@override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
+@override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',),
+                   USE_THOUSAND_SEPARATOR=True, USE_L10N=True)
 class DateHierarchyTests(TestCase):
     urls = "admin_views.urls"
     fixtures = ['admin-views-users.xml']
 
     def setUp(self):
         self.client.login(username='super', password='secret')
-        self.old_USE_THOUSAND_SEPARATOR = settings.USE_THOUSAND_SEPARATOR
-        self.old_USE_L10N = settings.USE_L10N
-        settings.USE_THOUSAND_SEPARATOR = True
-        settings.USE_L10N = True
 
     def tearDown(self):
-        settings.USE_THOUSAND_SEPARATOR = self.old_USE_THOUSAND_SEPARATOR
-        settings.USE_L10N = self.old_USE_L10N
         formats.reset_format_cache()
 
     def assert_non_localized_year(self, response, year):
diff --git a/tests/comment_tests/tests/test_comment_form.py b/tests/comment_tests/tests/test_comment_form.py
index bca339fd3d..205b4150e8 100644
--- a/tests/comment_tests/tests/test_comment_form.py
+++ b/tests/comment_tests/tests/test_comment_form.py
@@ -3,6 +3,7 @@ import time
 from django.conf import settings
 from django.contrib.comments.forms import CommentForm
 from django.contrib.comments.models import Comment
+from django.test.utils import override_settings
 
 from . import CommentTestCase
 from ..models import Article
@@ -58,26 +59,18 @@ class CommentFormTests(CommentTestCase):
         c.save()
         self.assertEqual(Comment.objects.count(), 1)
 
+    @override_settings(PROFANITIES_LIST=["rooster"])
     def testProfanities(self):
         """Test COMMENTS_ALLOW_PROFANITIES and PROFANITIES_LIST settings"""
         a = Article.objects.get(pk=1)
         d = self.getValidData(a)
 
-        # Save settings in case other tests need 'em
-        saved = settings.PROFANITIES_LIST, settings.COMMENTS_ALLOW_PROFANITIES
-
-        # Don't wanna swear in the unit tests if we don't have to...
-        settings.PROFANITIES_LIST = ["rooster"]
-
         # Try with COMMENTS_ALLOW_PROFANITIES off
-        settings.COMMENTS_ALLOW_PROFANITIES = False
-        f = CommentForm(a, data=dict(d, comment="What a rooster!"))
-        self.assertFalse(f.is_valid())
+        with self.settings(COMMENTS_ALLOW_PROFANITIES=False):
+            f = CommentForm(a, data=dict(d, comment="What a rooster!"))
+            self.assertFalse(f.is_valid())
 
         # Now with COMMENTS_ALLOW_PROFANITIES on
-        settings.COMMENTS_ALLOW_PROFANITIES = True
-        f = CommentForm(a, data=dict(d, comment="What a rooster!"))
-        self.assertTrue(f.is_valid())
-
-        # Restore settings
-        settings.PROFANITIES_LIST, settings.COMMENTS_ALLOW_PROFANITIES = saved
+        with self.settings(COMMENTS_ALLOW_PROFANITIES=True):
+            f = CommentForm(a, data=dict(d, comment="What a rooster!"))
+            self.assertTrue(f.is_valid())
diff --git a/tests/comment_tests/tests/test_comment_view.py b/tests/comment_tests/tests/test_comment_view.py
index 731776a1e2..653419d168 100644
--- a/tests/comment_tests/tests/test_comment_view.py
+++ b/tests/comment_tests/tests/test_comment_view.py
@@ -83,22 +83,19 @@ class CommentViewTests(CommentTestCase):
 
     def testDebugCommentErrors(self):
         """The debug error template should be shown only if DEBUG is True"""
-        olddebug = settings.DEBUG
-
-        settings.DEBUG = True
         a = Article.objects.get(pk=1)
         data = self.getValidData(a)
         data["security_hash"] = "Nobody expects the Spanish Inquisition!"
-        response = self.client.post("/post/", data)
-        self.assertEqual(response.status_code, 400)
-        self.assertTemplateUsed(response, "comments/400-debug.html")
 
-        settings.DEBUG = False
-        response = self.client.post("/post/", data)
-        self.assertEqual(response.status_code, 400)
-        self.assertTemplateNotUsed(response, "comments/400-debug.html")
+        with self.settings(DEBUG=True):
+            response = self.client.post("/post/", data)
+            self.assertEqual(response.status_code, 400)
+            self.assertTemplateUsed(response, "comments/400-debug.html")
 
-        settings.DEBUG = olddebug
+        with self.settings(DEBUG=False):
+            response = self.client.post("/post/", data)
+            self.assertEqual(response.status_code, 400)
+            self.assertTemplateNotUsed(response, "comments/400-debug.html")
 
     def testCreateValidComment(self):
         address = "1.2.3.4"
diff --git a/tests/generic_inline_admin/tests.py b/tests/generic_inline_admin/tests.py
index 2c90a13c4b..d56c7fb8e8 100644
--- a/tests/generic_inline_admin/tests.py
+++ b/tests/generic_inline_admin/tests.py
@@ -18,7 +18,8 @@ from .models import (Episode, EpisodeExtra, EpisodeMaxNum, Media,
     EpisodePermanent, Category)
 
 
-@override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
+@override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',),
+                   TEMPLATE_DEBUG=True)
 class GenericAdminViewTest(TestCase):
     urls = "generic_inline_admin.urls"
     fixtures = ['users.xml']
@@ -27,8 +28,7 @@ class GenericAdminViewTest(TestCase):
         # set TEMPLATE_DEBUG to True to ensure {% include %} will raise
         # exceptions since that is how inlines are rendered and #9498 will
         # bubble up if it is an issue.
-        self.original_template_debug = settings.TEMPLATE_DEBUG
-        settings.TEMPLATE_DEBUG = True
+
         self.client.login(username='super', password='secret')
 
         # Can't load content via a fixture (since the GenericForeignKey
@@ -46,7 +46,6 @@ class GenericAdminViewTest(TestCase):
 
     def tearDown(self):
         self.client.logout()
-        settings.TEMPLATE_DEBUG = self.original_template_debug
 
     def testBasicAddGet(self):
         """
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index b803d638ef..7cef9e1716 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -968,17 +968,9 @@ class ResolutionOrderI18NTests(TransRealMixin, TestCase):
         self.assertTrue(msgstr in result, ("The string '%s' isn't in the "
             "translation of '%s'; the actual result is '%s'." % (msgstr, msgid, result)))
 
+@override_settings(INSTALLED_APPS=['i18n.resolution'] + list(settings.INSTALLED_APPS))
 class AppResolutionOrderI18NTests(ResolutionOrderI18NTests):
 
-    def setUp(self):
-        self.old_installed_apps = settings.INSTALLED_APPS
-        settings.INSTALLED_APPS = ['i18n.resolution'] + list(settings.INSTALLED_APPS)
-        super(AppResolutionOrderI18NTests, self).setUp()
-
-    def tearDown(self):
-        settings.INSTALLED_APPS = self.old_installed_apps
-        super(AppResolutionOrderI18NTests, self).tearDown()
-
     def test_app_translation(self):
         self.assertUgettext('Date/time', 'APP')
 
diff --git a/tests/managers_regress/tests.py b/tests/managers_regress/tests.py
index 5534d670d7..f05e3e6085 100644
--- a/tests/managers_regress/tests.py
+++ b/tests/managers_regress/tests.py
@@ -6,6 +6,7 @@ from django.db import models
 from django.db.models.loading import cache
 from django.template import Context, Template
 from django.test import TestCase
+from django.test.utils import override_settings
 from django.utils.encoding import force_text
 
 from .models import (
@@ -108,6 +109,7 @@ class ManagersRegressionTests(TestCase):
         except AttributeError as e:
             self.assertEqual(str(e), "Manager isn't available; AbstractBase1 is abstract")
 
+    @override_settings(TEST_SWAPPABLE_MODEL='managers_regress.Parent')
     def test_swappable_manager(self):
         try:
             # This test adds dummy models to the app cache. These
@@ -116,8 +118,6 @@ class ManagersRegressionTests(TestCase):
             old_app_models = copy.deepcopy(cache.app_models)
             old_app_store = copy.deepcopy(cache.app_store)
 
-            settings.TEST_SWAPPABLE_MODEL = 'managers_regress.Parent'
-
             class SwappableModel(models.Model):
                 class Meta:
                     swappable = 'TEST_SWAPPABLE_MODEL'
@@ -131,10 +131,10 @@ class ManagersRegressionTests(TestCase):
                 self.assertEqual(str(e), "Manager isn't available; SwappableModel has been swapped for 'managers_regress.Parent'")
 
         finally:
-            del settings.TEST_SWAPPABLE_MODEL
             cache.app_models = old_app_models
             cache.app_store = old_app_store
 
+    @override_settings(TEST_SWAPPABLE_MODEL='managers_regress.Parent')
     def test_custom_swappable_manager(self):
         try:
             # This test adds dummy models to the app cache. These
@@ -143,8 +143,6 @@ class ManagersRegressionTests(TestCase):
             old_app_models = copy.deepcopy(cache.app_models)
             old_app_store = copy.deepcopy(cache.app_store)
 
-            settings.TEST_SWAPPABLE_MODEL = 'managers_regress.Parent'
-
             class SwappableModel(models.Model):
 
                 stuff = models.Manager()
@@ -162,10 +160,10 @@ class ManagersRegressionTests(TestCase):
                 self.assertEqual(str(e), "Manager isn't available; SwappableModel has been swapped for 'managers_regress.Parent'")
 
         finally:
-            del settings.TEST_SWAPPABLE_MODEL
             cache.app_models = old_app_models
             cache.app_store = old_app_store
 
+    @override_settings(TEST_SWAPPABLE_MODEL='managers_regress.Parent')
     def test_explicit_swappable_manager(self):
         try:
             # This test adds dummy models to the app cache. These
@@ -174,8 +172,6 @@ class ManagersRegressionTests(TestCase):
             old_app_models = copy.deepcopy(cache.app_models)
             old_app_store = copy.deepcopy(cache.app_store)
 
-            settings.TEST_SWAPPABLE_MODEL = 'managers_regress.Parent'
-
             class SwappableModel(models.Model):
 
                 objects = models.Manager()
@@ -193,7 +189,6 @@ class ManagersRegressionTests(TestCase):
                 self.assertEqual(str(e), "Manager isn't available; SwappableModel has been swapped for 'managers_regress.Parent'")
 
         finally:
-            del settings.TEST_SWAPPABLE_MODEL
             cache.app_models = old_app_models
             cache.app_store = old_app_store
 
diff --git a/tests/middleware_exceptions/tests.py b/tests/middleware_exceptions/tests.py
index fccfdbbd8c..e0f3729e9b 100644
--- a/tests/middleware_exceptions/tests.py
+++ b/tests/middleware_exceptions/tests.py
@@ -6,6 +6,7 @@ from django.http import HttpResponse
 from django.template.response import TemplateResponse
 from django.template import Template
 from django.test import TestCase
+from django.test.utils import override_settings
 
 class TestException(Exception):
     pass
@@ -772,15 +773,11 @@ _missing = object()
 class RootUrlconfTests(TestCase):
     urls = 'middleware_exceptions.urls'
 
+    @override_settings(ROOT_URLCONF=None)
     def test_missing_root_urlconf(self):
-        try:
-            original_ROOT_URLCONF = settings.ROOT_URLCONF
-            del settings.ROOT_URLCONF
-        except AttributeError:
-            original_ROOT_URLCONF = _missing
+        # Removing ROOT_URLCONF is safe, as override_settings will restore
+        # the previously defined settings.
+        del settings.ROOT_URLCONF
         self.assertRaises(AttributeError,
             self.client.get, "/middleware_exceptions/view/"
         )
-
-        if original_ROOT_URLCONF is not _missing:
-            settings.ROOT_URLCONF = original_ROOT_URLCONF
diff --git a/tests/modeladmin/tests.py b/tests/modeladmin/tests.py
index acc3c94271..df77202704 100644
--- a/tests/modeladmin/tests.py
+++ b/tests/modeladmin/tests.py
@@ -15,7 +15,7 @@ from django.core.exceptions import ImproperlyConfigured
 from django.forms.models import BaseModelFormSet
 from django.forms.widgets import Select
 from django.test import TestCase
-from django.test.utils import str_prefix
+from django.test.utils import str_prefix, override_settings
 from django.utils import six
 
 from .models import Band, Concert, ValidationTestModel, ValidationTestInlineModel
@@ -540,9 +540,7 @@ class ModelAdminTests(TestCase):
 class ValidationTests(unittest.TestCase):
     def test_validation_only_runs_in_debug(self):
         # Ensure validation only runs when DEBUG = True
-        try:
-            settings.DEBUG = True
-
+        with override_settings(DEBUG=True):
             class ValidationTestModelAdmin(ModelAdmin):
                 raw_id_fields = 10
 
@@ -555,11 +553,10 @@ class ValidationTests(unittest.TestCase):
                 ValidationTestModel,
                 ValidationTestModelAdmin,
             )
-        finally:
-            settings.DEBUG = False
 
-        site = AdminSite()
-        site.register(ValidationTestModel, ValidationTestModelAdmin)
+        with override_settings(DEBUG=False):
+            site = AdminSite()
+            site.register(ValidationTestModel, ValidationTestModelAdmin)
 
     def test_raw_id_fields_validation(self):
 
diff --git a/tests/proxy_models/tests.py b/tests/proxy_models/tests.py
index 2ee695929c..22ba47b84f 100644
--- a/tests/proxy_models/tests.py
+++ b/tests/proxy_models/tests.py
@@ -150,6 +150,7 @@ class ProxyModelTests(TestCase):
                     proxy = True
         self.assertRaises(FieldError, build_new_fields)
 
+    @override_settings(TEST_SWAPPABLE_MODEL='proxy_models.AlternateModel')
     def test_swappable(self):
         try:
             # This test adds dummy applications to the app cache. These
@@ -158,8 +159,6 @@ class ProxyModelTests(TestCase):
             old_app_models = copy.deepcopy(cache.app_models)
             old_app_store = copy.deepcopy(cache.app_store)
 
-            settings.TEST_SWAPPABLE_MODEL = 'proxy_models.AlternateModel'
-
             class SwappableModel(models.Model):
 
                 class Meta:
@@ -175,7 +174,6 @@ class ProxyModelTests(TestCase):
                     class Meta:
                         proxy = True
         finally:
-            del settings.TEST_SWAPPABLE_MODEL
             cache.app_models = old_app_models
             cache.app_store = old_app_store
 
diff --git a/tests/select_for_update/tests.py b/tests/select_for_update/tests.py
index b95a56fe4b..7147c97dcc 100644
--- a/tests/select_for_update/tests.py
+++ b/tests/select_for_update/tests.py
@@ -9,6 +9,7 @@ from django.db import transaction, connection, router
 from django.db.utils import ConnectionHandler, DEFAULT_DB_ALIAS, DatabaseError
 from django.test import (TransactionTestCase, skipIfDBFeature,
     skipUnlessDBFeature)
+from django.test.utils import override_settings
 
 from multiple_database.routers import TestRouter
 
@@ -23,6 +24,9 @@ except ImportError:
 requires_threading = unittest.skipUnless(threading, 'requires threading')
 
 
+# We need to set settings.DEBUG to True so we can capture the output SQL
+# to examine.
+@override_settings(DEBUG=True)
 class SelectForUpdateTests(TransactionTestCase):
 
     available_apps = ['select_for_update']
@@ -41,11 +45,6 @@ class SelectForUpdateTests(TransactionTestCase):
         self.new_connection = new_connections[DEFAULT_DB_ALIAS]
         self.new_connection.enter_transaction_management()
 
-        # We need to set settings.DEBUG to True so we can capture
-        # the output SQL to examine.
-        self._old_debug = settings.DEBUG
-        settings.DEBUG = True
-
     def tearDown(self):
         try:
             # We don't really care if this fails - some of the tests will set
@@ -55,7 +54,6 @@ class SelectForUpdateTests(TransactionTestCase):
         except transaction.TransactionManagementError:
             pass
         self.new_connection.close()
-        settings.DEBUG = self._old_debug
         try:
             self.end_blocking_transaction()
         except (DatabaseError, AttributeError):
diff --git a/tests/serializers/tests.py b/tests/serializers/tests.py
index a6b396fec1..30f775b9af 100644
--- a/tests/serializers/tests.py
+++ b/tests/serializers/tests.py
@@ -18,7 +18,7 @@ from django.conf import settings
 from django.core import management, serializers
 from django.db import transaction, connection
 from django.test import TestCase, TransactionTestCase
-from django.test.utils import Approximate
+from django.test.utils import Approximate, override_settings
 from django.utils import six
 from django.utils.six import StringIO
 
@@ -26,22 +26,18 @@ from .models import (Category, Author, Article, AuthorProfile, Actor, Movie,
     Score, Player, Team)
 
 
-class SerializerRegistrationTests(unittest.TestCase):
+@override_settings(
+    SERIALIZATION_MODULES = {
+        "json2" : "django.core.serializers.json",
+    }
+)
+class SerializerRegistrationTests(TestCase):
     def setUp(self):
-        self.old_SERIALIZATION_MODULES = getattr(settings, 'SERIALIZATION_MODULES', None)
         self.old_serializers = serializers._serializers
-
         serializers._serializers = {}
-        settings.SERIALIZATION_MODULES = {
-            "json2" : "django.core.serializers.json",
-        }
 
     def tearDown(self):
         serializers._serializers = self.old_serializers
-        if self.old_SERIALIZATION_MODULES:
-            settings.SERIALIZATION_MODULES = self.old_SERIALIZATION_MODULES
-        else:
-            delattr(settings, 'SERIALIZATION_MODULES')
 
     def test_register(self):
         "Registering a new serializer populates the full registry. Refs #14823"
diff --git a/tests/template_tests/test_loaders.py b/tests/template_tests/test_loaders.py
index ebdac4b9c4..1eef3942a6 100644
--- a/tests/template_tests/test_loaders.py
+++ b/tests/template_tests/test_loaders.py
@@ -23,6 +23,8 @@ except ImportError:
 from django.template import TemplateDoesNotExist, Context
 from django.template.loaders.eggs import Loader as EggLoader
 from django.template import loader
+from django.test import TestCase
+from django.test.utils import override_settings
 from django.utils import six
 from django.utils._os import upath
 from django.utils.six import StringIO
@@ -46,7 +48,8 @@ def create_egg(name, resources):
 
 
 @unittest.skipUnless(pkg_resources, 'setuptools is not installed')
-class EggLoaderTest(unittest.TestCase):
+@override_settings(INSTALLED_APPS=[])
+class EggLoaderTest(TestCase):
     def setUp(self):
         # Defined here b/c at module scope we may not have pkg_resources
         class MockProvider(pkg_resources.NullProvider):
@@ -73,51 +76,42 @@ class EggLoaderTest(unittest.TestCase):
             os.path.normcase('templates/y.html'): StringIO("y"),
             os.path.normcase('templates/x.txt'): StringIO("x"),
         })
-        self._old_installed_apps = settings.INSTALLED_APPS
-        settings.INSTALLED_APPS = []
-
-    def tearDown(self):
-        settings.INSTALLED_APPS = self._old_installed_apps
 
+    @override_settings(INSTALLED_APPS=['egg_empty'])
     def test_empty(self):
         "Loading any template on an empty egg should fail"
-        settings.INSTALLED_APPS = ['egg_empty']
         egg_loader = EggLoader()
         self.assertRaises(TemplateDoesNotExist, egg_loader.load_template_source, "not-existing.html")
 
+    @override_settings(INSTALLED_APPS=['egg_1'])
     def test_non_existing(self):
         "Template loading fails if the template is not in the egg"
-        settings.INSTALLED_APPS = ['egg_1']
         egg_loader = EggLoader()
         self.assertRaises(TemplateDoesNotExist, egg_loader.load_template_source, "not-existing.html")
 
+    @override_settings(INSTALLED_APPS=['egg_1'])
     def test_existing(self):
         "A template can be loaded from an egg"
-        settings.INSTALLED_APPS = ['egg_1']
         egg_loader = EggLoader()
         contents, template_name = egg_loader.load_template_source("y.html")
         self.assertEqual(contents, "y")
         self.assertEqual(template_name, "egg:egg_1:templates/y.html")
 
+    @override_settings(INSTALLED_APPS=[])
     def test_not_installed(self):
         "Loading an existent template from an egg not included in INSTALLED_APPS should fail"
-        settings.INSTALLED_APPS = []
         egg_loader = EggLoader()
         self.assertRaises(TemplateDoesNotExist, egg_loader.load_template_source, "y.html")
 
 
-class CachedLoader(unittest.TestCase):
-    def setUp(self):
-        self.old_TEMPLATE_LOADERS = settings.TEMPLATE_LOADERS
-        settings.TEMPLATE_LOADERS = (
-            ('django.template.loaders.cached.Loader', (
-                'django.template.loaders.filesystem.Loader',
-            )
-            ),
-        )
-    def tearDown(self):
-        settings.TEMPLATE_LOADERS = self.old_TEMPLATE_LOADERS
-
+@override_settings(
+    TEMPLATE_LOADERS = (
+        ('django.template.loaders.cached.Loader', (
+            'django.template.loaders.filesystem.Loader',
+        )),
+    )
+)
+class CachedLoader(TestCase):
     def test_templatedir_caching(self):
         "Check that the template directories form part of the template cache key. Refs #13573"
         # Retrive a template specifying a template directory to check
@@ -144,17 +138,12 @@ class CachedLoader(unittest.TestCase):
                          "Cached template loader doesn't cache file lookup misses. It should.")
 
 
-class RenderToStringTest(unittest.TestCase):
-
-    def setUp(self):
-        self._old_TEMPLATE_DIRS = settings.TEMPLATE_DIRS
-        settings.TEMPLATE_DIRS = (
-            os.path.join(os.path.dirname(upath(__file__)), 'templates'),
-        )
-
-    def tearDown(self):
-        settings.TEMPLATE_DIRS = self._old_TEMPLATE_DIRS
-
+@override_settings(
+    TEMPLATE_DIRS = (
+        os.path.join(os.path.dirname(upath(__file__)), 'templates'),
+    )
+)
+class RenderToStringTest(TestCase):
     def test_basic(self):
         self.assertEqual(loader.render_to_string('test_context.html'), 'obj:')
 
diff --git a/tests/template_tests/test_response.py b/tests/template_tests/test_response.py
index e8a9ee8a89..063fba3047 100644
--- a/tests/template_tests/test_response.py
+++ b/tests/template_tests/test_response.py
@@ -296,41 +296,30 @@ class TemplateResponseTest(TestCase):
         pickle.dumps(unpickled_response)
 
 
+@override_settings(
+    MIDDLEWARE_CLASSES=list(settings.MIDDLEWARE_CLASSES) + [
+        'template_tests.test_response.CustomURLConfMiddleware'
+    ]
+)
 class CustomURLConfTest(TestCase):
     urls = 'template_tests.urls'
 
-    def setUp(self):
-        self.old_MIDDLEWARE_CLASSES = settings.MIDDLEWARE_CLASSES
-        settings.MIDDLEWARE_CLASSES = list(settings.MIDDLEWARE_CLASSES) + [
-            'template_tests.test_response.CustomURLConfMiddleware'
-        ]
-
-    def tearDown(self):
-        settings.MIDDLEWARE_CLASSES = self.old_MIDDLEWARE_CLASSES
-
     def test_custom_urlconf(self):
         response = self.client.get('/template_response_view/')
         self.assertEqual(response.status_code, 200)
         self.assertContains(response, 'This is where you can find the snark: /snark/')
 
 
+@override_settings(
+    CACHE_MIDDLEWARE_SECONDS=2.0,
+    MIDDLEWARE_CLASSES=list(settings.MIDDLEWARE_CLASSES) + [
+        'django.middleware.cache.FetchFromCacheMiddleware',
+        'django.middleware.cache.UpdateCacheMiddleware',
+    ]
+)
 class CacheMiddlewareTest(TestCase):
     urls = 'template_tests.alternate_urls'
 
-    def setUp(self):
-        self.old_MIDDLEWARE_CLASSES = settings.MIDDLEWARE_CLASSES
-        self.CACHE_MIDDLEWARE_SECONDS = settings.CACHE_MIDDLEWARE_SECONDS
-
-        settings.CACHE_MIDDLEWARE_SECONDS = 2.0
-        settings.MIDDLEWARE_CLASSES = list(settings.MIDDLEWARE_CLASSES) + [
-            'django.middleware.cache.FetchFromCacheMiddleware',
-            'django.middleware.cache.UpdateCacheMiddleware',
-        ]
-
-    def tearDown(self):
-        settings.MIDDLEWARE_CLASSES = self.old_MIDDLEWARE_CLASSES
-        settings.CACHE_MIDDLEWARE_SECONDS = self.CACHE_MIDDLEWARE_SECONDS
-
     def test_middleware_caching(self):
         response = self.client.get('/template_response_view/')
         self.assertEqual(response.status_code, 200)
diff --git a/tests/template_tests/tests.py b/tests/template_tests/tests.py
index 98ca14ab42..ad6b4433da 100644
--- a/tests/template_tests/tests.py
+++ b/tests/template_tests/tests.py
@@ -201,10 +201,10 @@ class TemplateLoaderTests(TestCase):
             test_template_sources('/DIR1/index.HTML', template_dirs,
                                   ['/DIR1/index.HTML'])
 
+    # Turn TEMPLATE_DEBUG on, so that the origin file name will be kept with
+    # the compiled templates.
+    @override_settings(TEMPLATE_DEBUG=True)
     def test_loader_debug_origin(self):
-        # Turn TEMPLATE_DEBUG on, so that the origin file name will be kept with
-        # the compiled templates.
-        old_td, settings.TEMPLATE_DEBUG = settings.TEMPLATE_DEBUG, True
         old_loaders = loader.template_source_loaders
 
         try:
@@ -237,7 +237,6 @@ class TemplateLoaderTests(TestCase):
                 'Cached template loaded through cached loader has incorrect name for debug page: %s' % template_name)
         finally:
             loader.template_source_loaders = old_loaders
-            settings.TEMPLATE_DEBUG = old_td
 
     def test_loader_origin(self):
         with self.settings(TEMPLATE_DEBUG=True):
@@ -253,15 +252,14 @@ class TemplateLoaderTests(TestCase):
         template = loader.get_template('login.html')
         self.assertEqual(template.origin, None)
 
+    # TEMPLATE_DEBUG must be true, otherwise the exception raised
+    # during {% include %} processing will be suppressed.
+    @override_settings(TEMPLATE_DEBUG=True)
     def test_include_missing_template(self):
         """
         Tests that the correct template is identified as not existing
         when {% include %} specifies a template that does not exist.
         """
-
-        # TEMPLATE_DEBUG must be true, otherwise the exception raised
-        # during {% include %} processing will be suppressed.
-        old_td, settings.TEMPLATE_DEBUG = settings.TEMPLATE_DEBUG, True
         old_loaders = loader.template_source_loaders
 
         try:
@@ -276,13 +274,14 @@ class TemplateLoaderTests(TestCase):
                 tmpl = loader.select_template([load_name])
                 r = tmpl.render(template.Context({}))
             except template.TemplateDoesNotExist as e:
-                settings.TEMPLATE_DEBUG = old_td
                 self.assertEqual(e.args[0], 'missing.html')
             self.assertEqual(r, None, 'Template rendering unexpectedly succeeded, produced: ->%r<-' % r)
         finally:
             loader.template_source_loaders = old_loaders
-            settings.TEMPLATE_DEBUG = old_td
 
+    # TEMPLATE_DEBUG must be true, otherwise the exception raised
+    # during {% include %} processing will be suppressed.
+    @override_settings(TEMPLATE_DEBUG=True)
     def test_extends_include_missing_baseloader(self):
         """
         Tests that the correct template is identified as not existing
@@ -290,10 +289,6 @@ class TemplateLoaderTests(TestCase):
         that template has an {% include %} of something that does not
         exist. See #12787.
         """
-
-        # TEMPLATE_DEBUG must be true, otherwise the exception raised
-        # during {% include %} processing will be suppressed.
-        old_td, settings.TEMPLATE_DEBUG = settings.TEMPLATE_DEBUG, True
         old_loaders = loader.template_source_loaders
 
         try:
@@ -308,20 +303,18 @@ class TemplateLoaderTests(TestCase):
             try:
                 r = tmpl.render(template.Context({}))
             except template.TemplateDoesNotExist as e:
-                settings.TEMPLATE_DEBUG = old_td
                 self.assertEqual(e.args[0], 'missing.html')
             self.assertEqual(r, None, 'Template rendering unexpectedly succeeded, produced: ->%r<-' % r)
         finally:
             loader.template_source_loaders = old_loaders
-            settings.TEMPLATE_DEBUG = old_td
 
+    @override_settings(TEMPLATE_DEBUG=True)
     def test_extends_include_missing_cachedloader(self):
         """
         Same as test_extends_include_missing_baseloader, only tests
         behavior of the cached loader instead of BaseLoader.
         """
 
-        old_td, settings.TEMPLATE_DEBUG = settings.TEMPLATE_DEBUG, True
         old_loaders = loader.template_source_loaders
 
         try:
@@ -348,7 +341,6 @@ class TemplateLoaderTests(TestCase):
             self.assertEqual(r, None, 'Template rendering unexpectedly succeeded, produced: ->%r<-' % r)
         finally:
             loader.template_source_loaders = old_loaders
-            settings.TEMPLATE_DEBUG = old_td
 
     def test_include_template_argument(self):
         """
@@ -1822,17 +1814,15 @@ class TemplateTests(TransRealMixin, TestCase):
         return tests
 
 
-class TemplateTagLoading(unittest.TestCase):
+class TemplateTagLoading(TestCase):
 
     def setUp(self):
         self.old_path = sys.path[:]
-        self.old_apps = settings.INSTALLED_APPS
         self.egg_dir = '%s/eggs' % os.path.dirname(upath(__file__))
         self.old_tag_modules = template_base.templatetags_modules
         template_base.templatetags_modules = []
 
     def tearDown(self):
-        settings.INSTALLED_APPS = self.old_apps
         sys.path = self.old_path
         template_base.templatetags_modules = self.old_tag_modules
 
@@ -1845,11 +1835,11 @@ class TemplateTagLoading(unittest.TestCase):
             self.assertTrue('ImportError' in e.args[0])
             self.assertTrue('Xtemplate' in e.args[0])
 
+    @override_settings(INSTALLED_APPS=('tagsegg',))
     def test_load_error_egg(self):
         ttext = "{% load broken_egg %}"
         egg_name = '%s/tagsegg.egg' % self.egg_dir
         sys.path.append(egg_name)
-        settings.INSTALLED_APPS = ('tagsegg',)
         self.assertRaises(template.TemplateSyntaxError, template.Template, ttext)
         try:
             template.Template(ttext)
@@ -1857,11 +1847,11 @@ class TemplateTagLoading(unittest.TestCase):
             self.assertTrue('ImportError' in e.args[0])
             self.assertTrue('Xtemplate' in e.args[0])
 
+    @override_settings(INSTALLED_APPS=('tagsegg',))
     def test_load_working_egg(self):
         ttext = "{% load working_egg %}"
         egg_name = '%s/tagsegg.egg' % self.egg_dir
         sys.path.append(egg_name)
-        settings.INSTALLED_APPS = ('tagsegg',)
         template.Template(ttext)
 
 
diff --git a/tests/test_client/tests.py b/tests/test_client/tests.py
index 44a7851720..926d156303 100644
--- a/tests/test_client/tests.py
+++ b/tests/test_client/tests.py
@@ -467,17 +467,11 @@ class ClientTest(TestCase):
         self.assertEqual(mail.outbox[1].to[0], 'second@example.com')
         self.assertEqual(mail.outbox[1].to[1], 'third@example.com')
 
-class CSRFEnabledClientTests(TestCase):
-    def setUp(self):
-        # Enable the CSRF middleware for this test
-        self.old_MIDDLEWARE_CLASSES = settings.MIDDLEWARE_CLASSES
-        csrf_middleware_class = 'django.middleware.csrf.CsrfViewMiddleware'
-        if csrf_middleware_class not in settings.MIDDLEWARE_CLASSES:
-            settings.MIDDLEWARE_CLASSES += (csrf_middleware_class,)
-
-    def tearDown(self):
-        settings.MIDDLEWARE_CLASSES = self.old_MIDDLEWARE_CLASSES
 
+@override_settings(
+    MIDDLEWARE_CLASSES = ('django.middleware.csrf.CsrfViewMiddleware',)
+)
+class CSRFEnabledClientTests(TestCase):
     def test_csrf_enabled_client(self):
         "A client can be instantiated with CSRF checks enabled"
         csrf_client = Client(enforce_csrf_checks=True)
diff --git a/tests/urlpatterns_reverse/tests.py b/tests/urlpatterns_reverse/tests.py
index b2df2026d5..5305bd92b6 100644
--- a/tests/urlpatterns_reverse/tests.py
+++ b/tests/urlpatterns_reverse/tests.py
@@ -14,6 +14,7 @@ from django.core.urlresolvers import (reverse, reverse_lazy, resolve, get_callab
 from django.http import HttpRequest, HttpResponseRedirect, HttpResponsePermanentRedirect
 from django.shortcuts import redirect
 from django.test import TestCase
+from django.test.utils import override_settings
 from django.utils import six
 
 from . import urlconf_outer, middleware, views
@@ -453,16 +454,9 @@ class NamespaceTests(TestCase):
         self.assertEqual('/inc70/', reverse('inc-ns5:inner-nothing', args=['70']))
         self.assertEqual('/inc78/extra/foobar/', reverse('inc-ns5:inner-extra', args=['78','foobar']))
 
-class RequestURLconfTests(TestCase):
-    def setUp(self):
-        self.root_urlconf = settings.ROOT_URLCONF
-        self.middleware_classes = settings.MIDDLEWARE_CLASSES
-        settings.ROOT_URLCONF = urlconf_outer.__name__
-
-    def tearDown(self):
-        settings.ROOT_URLCONF = self.root_urlconf
-        settings.MIDDLEWARE_CLASSES = self.middleware_classes
 
+@override_settings(ROOT_URLCONF = urlconf_outer.__name__)
+class RequestURLconfTests(TestCase):
     def test_urlconf(self):
         response = self.client.get('/test/me/')
         self.assertEqual(response.status_code, 200)
@@ -473,10 +467,12 @@ class RequestURLconfTests(TestCase):
         response = self.client.get('/second_test/')
         self.assertEqual(response.status_code, 404)
 
-    def test_urlconf_overridden(self):
-        settings.MIDDLEWARE_CLASSES += (
+    @override_settings(
+        MIDDLEWARE_CLASSES=(
             '%s.ChangeURLconfMiddleware' % middleware.__name__,
         )
+    )
+    def test_urlconf_overridden(self):
         response = self.client.get('/test/me/')
         self.assertEqual(response.status_code, 404)
         response = self.client.get('/inner_urlconf/second_test/')
@@ -485,60 +481,70 @@ class RequestURLconfTests(TestCase):
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.content, b'outer:,inner:/second_test/')
 
-    def test_urlconf_overridden_with_null(self):
-        settings.MIDDLEWARE_CLASSES += (
+    @override_settings(
+        MIDDLEWARE_CLASSES=(
             '%s.NullChangeURLconfMiddleware' % middleware.__name__,
         )
+    )
+    def test_urlconf_overridden_with_null(self):
         self.assertRaises(ImproperlyConfigured, self.client.get, '/test/me/')
 
+    @override_settings(
+        MIDDLEWARE_CLASSES=(
+            '%s.ChangeURLconfMiddleware' % middleware.__name__,
+            '%s.ReverseInnerInResponseMiddleware' % middleware.__name__,
+        )
+    )
     def test_reverse_inner_in_response_middleware(self):
         """
         Test reversing an URL from the *overridden* URLconf from inside
         a response middleware.
         """
-        settings.MIDDLEWARE_CLASSES += (
-            '%s.ChangeURLconfMiddleware' % middleware.__name__,
-            '%s.ReverseInnerInResponseMiddleware' % middleware.__name__,
-        )
         response = self.client.get('/second_test/')
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.content, b'/second_test/')
 
+    @override_settings(
+        MIDDLEWARE_CLASSES=(
+            '%s.ChangeURLconfMiddleware' % middleware.__name__,
+            '%s.ReverseOuterInResponseMiddleware' % middleware.__name__,
+        )
+    )
     def test_reverse_outer_in_response_middleware(self):
         """
         Test reversing an URL from the *default* URLconf from inside
         a response middleware.
         """
-        settings.MIDDLEWARE_CLASSES += (
-            '%s.ChangeURLconfMiddleware' % middleware.__name__,
-            '%s.ReverseOuterInResponseMiddleware' % middleware.__name__,
-        )
         message = "Reverse for 'outer' with arguments '()' and keyword arguments '{}' not found."
         with self.assertRaisesMessage(NoReverseMatch, message):
             self.client.get('/second_test/')
 
+    @override_settings(
+        MIDDLEWARE_CLASSES=(
+            '%s.ChangeURLconfMiddleware' % middleware.__name__,
+            '%s.ReverseInnerInStreaming' % middleware.__name__,
+        )
+    )
     def test_reverse_inner_in_streaming(self):
         """
         Test reversing an URL from the *overridden* URLconf from inside
         a streaming response.
         """
-        settings.MIDDLEWARE_CLASSES += (
-            '%s.ChangeURLconfMiddleware' % middleware.__name__,
-            '%s.ReverseInnerInStreaming' % middleware.__name__,
-        )
         response = self.client.get('/second_test/')
         self.assertEqual(response.status_code, 200)
         self.assertEqual(b''.join(response), b'/second_test/')
 
+    @override_settings(
+        MIDDLEWARE_CLASSES=(
+            '%s.ChangeURLconfMiddleware' % middleware.__name__,
+            '%s.ReverseOuterInStreaming' % middleware.__name__,
+        )
+    )
     def test_reverse_outer_in_streaming(self):
         """
         Test reversing an URL from the *default* URLconf from inside
         a streaming response.
         """
-        settings.MIDDLEWARE_CLASSES += (
-            '%s.ChangeURLconfMiddleware' % middleware.__name__,
-            '%s.ReverseOuterInStreaming' % middleware.__name__,
-        )
         message = "Reverse for 'outer' with arguments '()' and keyword arguments '{}' not found."
         with self.assertRaisesMessage(NoReverseMatch, message):
             self.client.get('/second_test/')