[1.8.x] Refs #26253 -- Added tests for deprecation shims in SimpleTemplateResponse.

Backport of 3fedfc452f from stable/1.9.x

tests/template_tests/test_response_deprecations.py

@@ -0,0 +1,42 @@
+import warnings
+
+from django.http import HttpRequest
+from django.template import Template
+from django.template.response import TemplateResponse
+from django.test import SimpleTestCase
+
+
+class MyTemplateResponse(TemplateResponse):
+    def resolve_template(self, template_name):
+        return Template(template_name)
+
+
+class DeprecationTests(SimpleTestCase):
+
+    def test_template_response(self):
+        msg = (
+            "TemplateResponse's template argument cannot be a "
+            "django.template.Template anymore. It may be a backend-specific "
+            "template like those created by get_template()."
+        )
+        with warnings.catch_warnings(record=True) as warns:
+            warnings.simplefilter('always')
+            response = TemplateResponse(HttpRequest(), Template('foo'))
+        response.render()
+        self.assertEqual(response.content, b'foo')
+        self.assertEqual(len(warns), 1)
+        self.assertEqual(str(warns[0].message), msg)
+
+    def test_custom_template_response(self):
+        response = MyTemplateResponse(HttpRequest(), 'baz')
+        msg = (
+            "MyTemplateResponse.resolve_template() must return a "
+            "backend-specific template like those created by get_template(), "
+            "not a Template."
+        )
+        with warnings.catch_warnings(record=True) as warns:
+            warnings.simplefilter('always')
+            response.render()
+        self.assertEqual(response.content, b'baz')
+        self.assertEqual(len(warns), 1)
+        self.assertEqual(str(warns[0].message), msg)