2 files changed, 29 insertions, 1 deletions
diff --git a/tests/gis_tests/layermap/tests.py b/tests/gis_tests/layermap/tests.py
index 1ebeeb31c6..2406533e66 100644
--- a/tests/gis_tests/layermap/tests.py
+++ b/tests/gis_tests/layermap/tests.py
@@ -319,7 +319,10 @@ class OtherRouter:
         return self.db_for_read(model, **hints)
 
     def allow_relation(self, obj1, obj2, **hints):
-        return None
+        # ContentType objects are created during a post-migrate signal while
+        # performing fixture teardown using the default database alias and
+        # don't abide by the database specified by this router.
+        return True
 
     def allow_migrate(self, db, app_label, **hints):
         return True
diff --git a/tests/multiple_database/tests.py b/tests/multiple_database/tests.py
index 6dd44f6475..e4cef8cdb9 100644
--- a/tests/multiple_database/tests.py
+++ b/tests/multiple_database/tests.py
@@ -2082,3 +2082,28 @@ class RouteForWriteTestCase(TestCase):
         self.assertEqual(e.mode, RouterUsed.WRITE)
         self.assertEqual(e.model, Book)
         self.assertEqual(e.hints, {'instance': auth})
+
+
+class NoRelationRouter:
+    """Disallow all relations."""
+    def allow_relation(self, obj1, obj2, **hints):
+        return False
+
+
+@override_settings(DATABASE_ROUTERS=[NoRelationRouter()])
+class RelationAssignmentTests(TestCase):
+    """allow_relation() is called with unsaved model instances."""
+    multi_db = True
+    router_prevents_msg = 'the current database router prevents this relation'
+
+    def test_foreign_key_relation(self):
+        person = Person(name='Someone')
+        pet = Pet()
+        with self.assertRaisesMessage(ValueError, self.router_prevents_msg):
+            pet.owner = person
+
+    def test_reverse_one_to_one_relation(self):
+        user = User(username='Someone', password='fake_hash')
+        profile = UserProfile()
+        with self.assertRaisesMessage(ValueError, self.router_prevents_msg):
+            user.userprofile = profile