Replaced router.routers usage with override_settings(DATABASE_ROUTERS); refs #23933.

7 files changed, 121 insertions, 214 deletions

diff --git a/django/contrib/gis/tests/layermap/tests.py b/django/contrib/gis/tests/layermap/tests.py
index b9b1404b3c..45709e30ce 100644
--- a/django/contrib/gis/tests/layermap/tests.py
+++ b/django/contrib/gis/tests/layermap/tests.py
@@ -8,9 +8,9 @@ import unittest
 from unittest import skipUnless
 
 from django.contrib.gis.gdal import HAS_GDAL
-from django.db import connection, router
+from django.db import connection
 from django.conf import settings
-from django.test import TestCase, skipUnlessDBFeature
+from django.test import TestCase, override_settings, skipUnlessDBFeature
 from django.utils._os import upath
 
 if HAS_GDAL:
@@ -328,15 +328,9 @@ class OtherRouter(object):
 
 @skipUnless(HAS_GDAL, "LayerMapRouterTest needs GDAL support")
 @skipUnlessDBFeature("gis_enabled")
+@override_settings(DATABASE_ROUTERS=[OtherRouter()])
 class LayerMapRouterTest(TestCase):
 
-    def setUp(self):
-        self.old_routers = router.routers
-        router.routers = [OtherRouter()]
-
-    def tearDown(self):
-        router.routers = self.old_routers
-
     @unittest.skipUnless(len(settings.DATABASES) > 1, 'multiple databases required')
     def test_layermapping_default_db(self):
         lm = LayerMapping(City, city_shp, city_mapping)
diff --git a/tests/cache/tests.py b/tests/cache/tests.py
index 9dfd7af15d..e3ad724a86 100644
--- a/tests/cache/tests.py
+++ b/tests/cache/tests.py
@@ -19,7 +19,7 @@ from django.core import management
 from django.core.cache import (cache, caches, CacheKeyWarning,
     InvalidCacheBackendError, DEFAULT_CACHE_ALIAS)
 from django.core.context_processors import csrf
-from django.db import connection, connections, router, transaction
+from django.db import connection, connections, transaction
 from django.core.cache.utils import make_template_fragment_key
 from django.http import HttpResponse, StreamingHttpResponse
 from django.middleware.cache import (FetchFromCacheMiddleware,
@@ -974,29 +974,25 @@ class DBCacheRouter(object):
 class CreateCacheTableForDBCacheTests(TestCase):
     multi_db = True
 
+    @override_settings(DATABASE_ROUTERS=[DBCacheRouter()])
     def test_createcachetable_observes_database_router(self):
-        old_routers = router.routers
-        try:
-            router.routers = [DBCacheRouter()]
-            # cache table should not be created on 'default'
-            with self.assertNumQueries(0, using='default'):
-                management.call_command('createcachetable',
-                                        database='default',
-                                        verbosity=0, interactive=False)
-            # cache table should be created on 'other'
-            # Queries:
-            #   1: check table doesn't already exist
-            #   2: create savepoint (if transactional DDL is supported)
-            #   3: create the table
-            #   4: create the index
-            #   5: release savepoint (if transactional DDL is supported)
-            num = 5 if connections['other'].features.can_rollback_ddl else 3
-            with self.assertNumQueries(num, using='other'):
-                management.call_command('createcachetable',
-                                        database='other',
-                                        verbosity=0, interactive=False)
-        finally:
-            router.routers = old_routers
+        # cache table should not be created on 'default'
+        with self.assertNumQueries(0, using='default'):
+            management.call_command('createcachetable',
+                                    database='default',
+                                    verbosity=0, interactive=False)
+        # cache table should be created on 'other'
+        # Queries:
+        #   1: check table doesn't already exist
+        #   2: create savepoint (if transactional DDL is supported)
+        #   3: create the table
+        #   4: create the index
+        #   5: release savepoint (if transactional DDL is supported)
+        num = 5 if connections['other'].features.can_rollback_ddl else 3
+        with self.assertNumQueries(num, using='other'):
+            management.call_command('createcachetable',
+                                    database='other',
+                                    verbosity=0, interactive=False)
 
 
 class PicklingSideEffect(object):
diff --git a/tests/commands_sql/tests.py b/tests/commands_sql/tests.py
index e9499d6b05..e381c031a5 100644
--- a/tests/commands_sql/tests.py
+++ b/tests/commands_sql/tests.py
@@ -7,8 +7,8 @@ from django.apps import apps
 from django.core.management.color import no_style
 from django.core.management.sql import (sql_create, sql_delete, sql_indexes,
     sql_destroy_indexes, sql_all)
-from django.db import connections, DEFAULT_DB_ALIAS, router
-from django.test import TestCase
+from django.db import connections, DEFAULT_DB_ALIAS
+from django.test import TestCase, override_settings
 from django.utils import six
 
 # See also initial_sql_regress for 'custom_sql_for_model' tests
@@ -91,13 +91,8 @@ class TestRouter(object):
         return False
 
 
+@override_settings(DATABASE_ROUTERS=[TestRouter()])
 class SQLCommandsRouterTestCase(TestCase):
-    def setUp(self):
-        self._old_routers = router.routers
-        router.routers = [TestRouter()]
-
-    def tearDown(self):
-        router.routers = self._old_routers
 
     def test_router_honored(self):
         app_config = apps.get_app_config('commands_sql')
diff --git a/tests/contenttypes_tests/tests.py b/tests/contenttypes_tests/tests.py
index a21d783008..0e33f40c5c 100644
--- a/tests/contenttypes_tests/tests.py
+++ b/tests/contenttypes_tests/tests.py
@@ -8,9 +8,9 @@ from django.contrib.contenttypes.fields import (
 from django.contrib.contenttypes import management
 from django.contrib.contenttypes.models import ContentType
 from django.core import checks
-from django.db import connections, models, router
-from django.test import TestCase
-from django.test.utils import captured_stdout, override_settings
+from django.db import connections, models
+from django.test import TestCase, override_settings
+from django.test.utils import captured_stdout
 from django.utils.encoding import force_str
 
 from .models import Author, Article, SchemeIncludedURL
@@ -397,12 +397,10 @@ class TestRouter(object):
         return 'default'
 
 
+@override_settings(DATABASE_ROUTERS=[TestRouter()])
 class ContentTypesMultidbTestCase(TestCase):
 
     def setUp(self):
-        self.old_routers = router.routers
-        router.routers = [TestRouter()]
-
         # Whenever a test starts executing, only the "default" database is
         # connected. We explicitly connect to the "other" database here. If we
         # don't do it, then it will be implicitly connected later when we query
@@ -411,9 +409,6 @@ class ContentTypesMultidbTestCase(TestCase):
         # "SET SQL_AUTO_IS_NULL = 0"), which will affect assertNumQueries().
         connections['other'].ensure_connection()
 
-    def tearDown(self):
-        router.routers = self.old_routers
-
     def test_multidb(self):
         """
         Test that, when using multiple databases, we use the db_for_read (see
diff --git a/tests/migrations/test_operations.py b/tests/migrations/test_operations.py
index ef6cbfc688..b08bdbc489 100644
--- a/tests/migrations/test_operations.py
+++ b/tests/migrations/test_operations.py
@@ -8,13 +8,13 @@ except ImportError:
     sqlparse = None
 
 from django import test
-from django.test import override_settings
-from django.db import connection, migrations, models, router
+from django.db import connection, migrations, models
 from django.db.migrations.migration import Migration
 from django.db.migrations.state import ProjectState
 from django.db.models.fields import NOT_PROVIDED
 from django.db.transaction import atomic
 from django.db.utils import IntegrityError, DatabaseError
+from django.test import override_settings
 from django.utils import six
 
 from .test_base import MigrationTestBase
@@ -1566,18 +1566,10 @@ class MigrateNothingRouter(object):
         return False
 
 
+@override_settings(DATABASE_ROUTERS=[MigrateNothingRouter()])
 class MultiDBOperationTests(MigrationTestBase):
     multi_db = True
 
-    def setUp(self):
-        # Make the 'other' database appear to be a replica of the 'default'
-        self.old_routers = router.routers
-        router.routers = [MigrateNothingRouter()]
-
-    def tearDown(self):
-        # Restore the 'other' database as an independent database
-        router.routers = self.old_routers
-
     def test_create_model(self):
         """
         Tests that CreateModel honours multi-db settings.
diff --git a/tests/multiple_database/tests.py b/tests/multiple_database/tests.py
index 17a1ef90b1..90e418ba15 100644
--- a/tests/multiple_database/tests.py
+++ b/tests/multiple_database/tests.py
@@ -883,18 +883,11 @@ class ConnectionRouterTestCase(TestCase):
                              ['TestRouter', 'WriteRouter'])
 
 
+# Make the 'other' database appear to be a replica of the 'default'
+@override_settings(DATABASE_ROUTERS=[TestRouter()])
 class RouterTestCase(TestCase):
     multi_db = True
 
-    def setUp(self):
-        # Make the 'other' database appear to be a replica of the 'default'
-        self.old_routers = router.routers
-        router.routers = [TestRouter()]
-
-    def tearDown(self):
-        # Restore the 'other' database as an independent database
-        router.routers = self.old_routers
-
     def test_db_selection(self):
         "Check that querysets obey the router for db suggestions"
         self.assertEqual(Book.objects.db, 'other')
@@ -914,24 +907,22 @@ class RouterTestCase(TestCase):
         self.assertTrue(router.allow_migrate('other', User))
         self.assertTrue(router.allow_migrate('other', Book))
 
-        # Add the auth router to the chain.
-        # TestRouter is a universal synchronizer, so it should have no effect.
-        router.routers = [TestRouter(), AuthRouter()]
-
-        self.assertTrue(router.allow_migrate('default', User))
-        self.assertTrue(router.allow_migrate('default', Book))
-
-        self.assertTrue(router.allow_migrate('other', User))
-        self.assertTrue(router.allow_migrate('other', Book))
+        with override_settings(DATABASE_ROUTERS=[TestRouter(), AuthRouter()]):
+            # Add the auth router to the chain. TestRouter is a universal
+            # synchronizer, so it should have no effect.
+            self.assertTrue(router.allow_migrate('default', User))
+            self.assertTrue(router.allow_migrate('default', Book))
 
-        # Now check what happens if the router order is the other way around
-        router.routers = [AuthRouter(), TestRouter()]
+            self.assertTrue(router.allow_migrate('other', User))
+            self.assertTrue(router.allow_migrate('other', Book))
 
-        self.assertFalse(router.allow_migrate('default', User))
-        self.assertTrue(router.allow_migrate('default', Book))
+        with override_settings(DATABASE_ROUTERS=[AuthRouter(), TestRouter()]):
+            # Now check what happens if the router order is reversed.
+            self.assertFalse(router.allow_migrate('default', User))
+            self.assertTrue(router.allow_migrate('default', Book))
 
-        self.assertTrue(router.allow_migrate('other', User))
-        self.assertFalse(router.allow_migrate('other', Book))
+            self.assertTrue(router.allow_migrate('other', User))
+            self.assertFalse(router.allow_migrate('other', Book))
 
     def test_partial_router(self):
         "A router can choose to implement a subset of methods"
@@ -951,18 +942,17 @@ class RouterTestCase(TestCase):
         self.assertTrue(router.allow_migrate('default', User))
         self.assertTrue(router.allow_migrate('default', Book))
 
-        router.routers = [WriteRouter(), AuthRouter(), TestRouter()]
-
-        self.assertEqual(router.db_for_read(User), 'default')
-        self.assertEqual(router.db_for_read(Book), 'other')
+        with override_settings(DATABASE_ROUTERS=[WriteRouter(), AuthRouter(), TestRouter()]):
+            self.assertEqual(router.db_for_read(User), 'default')
+            self.assertEqual(router.db_for_read(Book), 'other')
 
-        self.assertEqual(router.db_for_write(User), 'writer')
-        self.assertEqual(router.db_for_write(Book), 'writer')
+            self.assertEqual(router.db_for_write(User), 'writer')
+            self.assertEqual(router.db_for_write(Book), 'writer')
 
-        self.assertTrue(router.allow_relation(dive, dive))
+            self.assertTrue(router.allow_relation(dive, dive))
 
-        self.assertFalse(router.allow_migrate('default', User))
-        self.assertTrue(router.allow_migrate('default', Book))
+            self.assertFalse(router.allow_migrate('default', User))
+            self.assertTrue(router.allow_migrate('default', Book))
 
     def test_database_routing(self):
         marty = Person.objects.using('default').create(name="Marty Alchin")
@@ -1447,18 +1437,10 @@ class RouterTestCase(TestCase):
                          datetime.date(2009, 5, 4))
 
 
+@override_settings(DATABASE_ROUTERS=[AuthRouter()])
 class AuthTestCase(TestCase):
     multi_db = True
 
-    def setUp(self):
-        # Make the 'other' database appear to be a replica of the 'default'
-        self.old_routers = router.routers
-        router.routers = [AuthRouter()]
-
-    def tearDown(self):
-        # Restore the 'other' database as an independent database
-        router.routers = self.old_routers
-
     def test_auth_manager(self):
         "The methods on the auth manager obey database hints"
         # Create one user using default allocation policy
@@ -1522,15 +1504,7 @@ class FixtureTestCase(TestCase):
     multi_db = True
     fixtures = ['multidb-common', 'multidb']
 
-    def setUp(self):
-        # Install the anti-pet router
-        self.old_routers = router.routers
-        router.routers = [AntiPetRouter()]
-
-    def tearDown(self):
-        # Restore the 'other' database as an independent database
-        router.routers = self.old_routers
-
+    @override_settings(DATABASE_ROUTERS=[AntiPetRouter()])
     def test_fixture_loading(self):
         "Multi-db fixtures are loaded correctly"
         # Check that "Pro Django" exists on the default database, but not on other database
@@ -1571,6 +1545,7 @@ class FixtureTestCase(TestCase):
         except Book.DoesNotExist:
             self.fail('"The Definitive Guide to Django" should exist on both databases')
 
+    @override_settings(DATABASE_ROUTERS=[AntiPetRouter()])
     def test_pseudo_empty_fixtures(self):
         "A fixture can contain entries, but lead to nothing in the database; this shouldn't raise an error (ref #14068)"
         new_io = StringIO()
@@ -1609,19 +1584,8 @@ class WriteToOtherRouter(object):
 class SignalTests(TestCase):
     multi_db = True
 
-    def setUp(self):
-        self.old_routers = router.routers
-
-    def tearDown(self):
-        router.routers = self.old_routers
-
-    def _write_to_other(self):
-        "Sends all writes to 'other'."
-        router.routers = [WriteToOtherRouter()]
-
-    def _write_to_default(self):
-        "Sends all writes to the default DB"
-        router.routers = self.old_routers
+    def override_router(self):
+        return override_settings(DATABASE_ROUTERS=[WriteToOtherRouter()])
 
     def test_database_arg_save_and_delete(self):
         """
@@ -1684,33 +1648,29 @@ class SignalTests(TestCase):
         # Test addition
         b.authors.add(p)
         self.assertEqual(receiver._database, DEFAULT_DB_ALIAS)
-        self._write_to_other()
-        b.authors.add(p)
-        self._write_to_default()
+        with self.override_router():
+            b.authors.add(p)
         self.assertEqual(receiver._database, "other")
 
         # Test removal
         b.authors.remove(p)
         self.assertEqual(receiver._database, DEFAULT_DB_ALIAS)
-        self._write_to_other()
-        b.authors.remove(p)
-        self._write_to_default()
+        with self.override_router():
+            b.authors.remove(p)
         self.assertEqual(receiver._database, "other")
 
         # Test addition in reverse
         p.book_set.add(b)
         self.assertEqual(receiver._database, DEFAULT_DB_ALIAS)
-        self._write_to_other()
-        p.book_set.add(b)
-        self._write_to_default()
+        with self.override_router():
+            p.book_set.add(b)
         self.assertEqual(receiver._database, "other")
 
         # Test clearing
         b.authors.clear()
         self.assertEqual(receiver._database, DEFAULT_DB_ALIAS)
-        self._write_to_other()
-        b.authors.clear()
-        self._write_to_default()
+        with self.override_router():
+            b.authors.clear()
         self.assertEqual(receiver._database, "other")
 
 
@@ -1726,47 +1686,41 @@ class AttributeErrorRouter(object):
 class RouterAttributeErrorTestCase(TestCase):
     multi_db = True
 
-    def setUp(self):
-        self.old_routers = router.routers
-        router.routers = [AttributeErrorRouter()]
-
-    def tearDown(self):
-        router.routers = self.old_routers
+    def override_router(self):
+        return override_settings(DATABASE_ROUTERS=[AttributeErrorRouter()])
 
     def test_attribute_error_read(self):
         "Check that the AttributeError from AttributeErrorRouter bubbles up"
-        router.routers = []  # Reset routers so we can save a Book instance
         b = Book.objects.create(title="Pro Django",
                                 published=datetime.date(2008, 12, 16))
-        router.routers = [AttributeErrorRouter()]  # Install our router
-        self.assertRaises(AttributeError, Book.objects.get, pk=b.pk)
+        with self.override_router():
+            self.assertRaises(AttributeError, Book.objects.get, pk=b.pk)
 
     def test_attribute_error_save(self):
         "Check that the AttributeError from AttributeErrorRouter bubbles up"
         dive = Book()
         dive.title = "Dive into Python"
         dive.published = datetime.date(2009, 5, 4)
-        self.assertRaises(AttributeError, dive.save)
+        with self.override_router():
+            self.assertRaises(AttributeError, dive.save)
 
     def test_attribute_error_delete(self):
         "Check that the AttributeError from AttributeErrorRouter bubbles up"
-        router.routers = []  # Reset routers so we can save our Book, Person instances
         b = Book.objects.create(title="Pro Django",
                                 published=datetime.date(2008, 12, 16))
         p = Person.objects.create(name="Marty Alchin")
         b.authors = [p]
         b.editor = p
-        router.routers = [AttributeErrorRouter()]  # Install our router
-        self.assertRaises(AttributeError, b.delete)
+        with self.override_router():
+            self.assertRaises(AttributeError, b.delete)
 
     def test_attribute_error_m2m(self):
         "Check that the AttributeError from AttributeErrorRouter bubbles up"
-        router.routers = []  # Reset routers so we can save our Book, Person instances
         b = Book.objects.create(title="Pro Django",
                                 published=datetime.date(2008, 12, 16))
         p = Person.objects.create(name="Marty Alchin")
-        router.routers = [AttributeErrorRouter()]  # Install our router
-        self.assertRaises(AttributeError, setattr, b, 'authors', [p])
+        with self.override_router():
+            self.assertRaises(AttributeError, setattr, b, 'authors', [p])
 
 
 class ModelMetaRouter(object):
@@ -1776,16 +1730,10 @@ class ModelMetaRouter(object):
             raise ValueError
 
 
+@override_settings(DATABASE_ROUTERS=[ModelMetaRouter()])
 class RouterModelArgumentTestCase(TestCase):
     multi_db = True
 
-    def setUp(self):
-        self.old_routers = router.routers
-        router.routers = [ModelMetaRouter()]
-
-    def tearDown(self):
-        router.routers = self.old_routers
-
     def test_m2m_collection(self):
         b = Book.objects.create(title="Pro Django",
                                 published=datetime.date(2008, 12, 16))
@@ -1840,13 +1788,9 @@ class MigrateTestCase(TestCase):
         cts = ContentType.objects.using('other').filter(app_label='multiple_database')
 
         cts.delete()
-        try:
-            old_routers = router.routers
-            router.routers = [SyncOnlyDefaultDatabaseRouter()]
+        with override_settings(DATABASE_ROUTERS=[SyncOnlyDefaultDatabaseRouter()]):
             management.call_command('migrate', verbosity=0, interactive=False,
                 load_initial_data=False, database='other')
-        finally:
-            router.routers = old_routers
 
         self.assertEqual(cts.count(), 0)
 
@@ -1868,21 +1812,15 @@ class RouteForWriteTestCase(TestCase):
         def db_for_write(self, model, **hints):
             raise RouterUsed(mode=RouterUsed.WRITE, model=model, hints=hints)
 
-    def setUp(self):
-        self._old_rtrs = router.routers
-
-    def tearDown(self):
-        router.routers = self._old_rtrs
-
-    def enable_router(self):
-        router.routers = [RouteForWriteTestCase.WriteCheckRouter()]
+    def override_router(self):
+        return override_settings(DATABASE_ROUTERS=[RouteForWriteTestCase.WriteCheckRouter()])
 
     def test_fk_delete(self):
         owner = Person.objects.create(name='Someone')
         pet = Pet.objects.create(name='fido', owner=owner)
-        self.enable_router()
         try:
-            pet.owner.delete()
+            with self.override_router():
+                pet.owner.delete()
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1892,9 +1830,9 @@ class RouteForWriteTestCase(TestCase):
     def test_reverse_fk_delete(self):
         owner = Person.objects.create(name='Someone')
         to_del_qs = owner.pet_set.all()
-        self.enable_router()
         try:
-            to_del_qs.delete()
+            with self.override_router():
+                to_del_qs.delete()
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1903,9 +1841,9 @@ class RouteForWriteTestCase(TestCase):
 
     def test_reverse_fk_get_or_create(self):
         owner = Person.objects.create(name='Someone')
-        self.enable_router()
         try:
-            owner.pet_set.get_or_create(name='fido')
+            with self.override_router():
+                owner.pet_set.get_or_create(name='fido')
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1915,9 +1853,9 @@ class RouteForWriteTestCase(TestCase):
     def test_reverse_fk_update(self):
         owner = Person.objects.create(name='Someone')
         Pet.objects.create(name='fido', owner=owner)
-        self.enable_router()
         try:
-            owner.pet_set.update(name='max')
+            with self.override_router():
+                owner.pet_set.update(name='max')
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1928,9 +1866,9 @@ class RouteForWriteTestCase(TestCase):
         auth = Person.objects.create(name='Someone')
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
-        self.enable_router()
         try:
-            book.authors.add(auth)
+            with self.override_router():
+                book.authors.add(auth)
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1942,9 +1880,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            book.authors.clear()
+            with self.override_router():
+                book.authors.clear()
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1956,9 +1894,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            book.authors.all().delete()
+            with self.override_router():
+                book.authors.all().delete()
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1969,9 +1907,9 @@ class RouteForWriteTestCase(TestCase):
         Person.objects.create(name='Someone')
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
-        self.enable_router()
         try:
-            book.authors.get_or_create(name='Someone else')
+            with self.override_router():
+                book.authors.get_or_create(name='Someone else')
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1983,10 +1921,10 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         self.assertRaisesMessage(AttributeError, self.RAISE_MSG, )
         try:
-            book.authors.remove(auth)
+            with self.override_router():
+                book.authors.remove(auth)
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -1998,9 +1936,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            book.authors.all().update(name='Different')
+            with self.override_router():
+                book.authors.all().update(name='Different')
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -2011,9 +1949,9 @@ class RouteForWriteTestCase(TestCase):
         auth = Person.objects.create(name='Someone')
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
-        self.enable_router()
         try:
-            auth.book_set.add(book)
+            with self.override_router():
+                auth.book_set.add(book)
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -2025,9 +1963,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            auth.book_set.clear()
+            with self.override_router():
+                auth.book_set.clear()
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -2039,9 +1977,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            auth.book_set.all().delete()
+            with self.override_router():
+                auth.book_set.all().delete()
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -2052,9 +1990,9 @@ class RouteForWriteTestCase(TestCase):
         auth = Person.objects.create(name='Someone')
         Book.objects.create(title="Pro Django",
                             published=datetime.date(2008, 12, 16))
-        self.enable_router()
         try:
-            auth.book_set.get_or_create(title="New Book", published=datetime.datetime.now())
+            with self.override_router():
+                auth.book_set.get_or_create(title="New Book", published=datetime.datetime.now())
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -2066,9 +2004,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            auth.book_set.remove(book)
+            with self.override_router():
+                auth.book_set.remove(book)
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
@@ -2080,9 +2018,9 @@ class RouteForWriteTestCase(TestCase):
         book = Book.objects.create(title="Pro Django",
                                    published=datetime.date(2008, 12, 16))
         book.authors.add(auth)
-        self.enable_router()
         try:
-            auth.book_set.all().update(title='Different')
+            with self.override_router():
+                auth.book_set.all().update(title='Different')
             self.fail('db_for_write() not invoked on router')
         except RouterUsed as e:
             self.assertEqual(e.mode, RouterUsed.WRITE)
diff --git a/tests/select_for_update/tests.py b/tests/select_for_update/tests.py
index a0bd206923..d3f71ab65c 100644
--- a/tests/select_for_update/tests.py
+++ b/tests/select_for_update/tests.py
@@ -6,9 +6,10 @@ import unittest
 from django.conf import settings
 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 import override_settings
+from django.test import (
+    TransactionTestCase, override_settings, skipIfDBFeature,
+    skipUnlessDBFeature,
+)
 
 from multiple_database.routers import TestRouter
 
@@ -257,14 +258,10 @@ class SelectForUpdateTests(TransactionTestCase):
         self.assertIsInstance(status[-1], DatabaseError)
 
     @skipUnlessDBFeature('has_select_for_update')
+    @override_settings(DATABASE_ROUTERS=[TestRouter()])
     def test_select_for_update_on_multidb(self):
-        old_routers = router.routers
-        try:
-            router.routers = [TestRouter()]
-            query = Person.objects.select_for_update()
-            self.assertEqual(router.db_for_write(Person), query.db)
-        finally:
-            router.routers = old_routers
+        query = Person.objects.select_for_update()
+        self.assertEqual(router.db_for_write(Person), query.db)
 
     @skipUnlessDBFeature('has_select_for_update')
     def test_select_for_update_with_get(self):