Refs #26601 -- Deprecated passing None as get_response arg to middleware classes.

This is the new contract since middleware refactoring in Django 1.10.

Co-authored-by: Carlton Gibson <carlton.gibson@noumenal.es>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/tests/deprecation/test_middleware_mixin.py b/tests/deprecation/test_middleware_mixin.py
new file mode 100644
index 0000000000..f03d9168ec
--- /dev/null
+++ b/tests/deprecation/test_middleware_mixin.py
@@ -0,0 +1,39 @@
+from django.contrib.sessions.middleware import SessionMiddleware
+from django.middleware.cache import (
+    CacheMiddleware, FetchFromCacheMiddleware, UpdateCacheMiddleware,
+)
+from django.middleware.common import CommonMiddleware
+from django.middleware.security import SecurityMiddleware
+from django.test import SimpleTestCase
+from django.utils.deprecation import RemovedInDjango40Warning
+
+
+class MiddlewareMixinTests(SimpleTestCase):
+    """
+    Deprecation warning is raised when using get_response=None.
+    """
+    msg = 'Passing None for the middleware get_response argument is deprecated.'
+
+    def test_deprecation(self):
+        with self.assertRaisesMessage(RemovedInDjango40Warning, self.msg):
+            CommonMiddleware()
+
+    def test_passing_explicit_none(self):
+        with self.assertRaisesMessage(RemovedInDjango40Warning, self.msg):
+            CommonMiddleware(None)
+
+    def test_subclass_deprecation(self):
+        """
+        Deprecation warning is raised in subclasses overriding __init__()
+        without calling super().
+        """
+        for middleware in [
+            SessionMiddleware,
+            CacheMiddleware,
+            FetchFromCacheMiddleware,
+            UpdateCacheMiddleware,
+            SecurityMiddleware,
+        ]:
+            with self.subTest(middleware=middleware):
+                with self.assertRaisesMessage(RemovedInDjango40Warning, self.msg):
+                    middleware()