feat: add branded error pages

backend/workflows/tests/error_test_urls.py

@@ -0,0 +1,28 @@
+from django.core.exceptions import PermissionDenied
+from django.http import HttpResponse
+from django.urls import include, path
+
+
+def ok_view(request):
+    return HttpResponse('ok')
+
+
+def deny_view(request):
+    raise PermissionDenied('forbidden')
+
+
+def explode_view(request):
+    raise RuntimeError('boom')
+
+
+handler400 = 'workflows.error_views.bad_request'
+handler403 = 'workflows.error_views.permission_denied'
+handler404 = 'workflows.error_views.not_found'
+handler500 = 'workflows.error_views.server_error'
+
+urlpatterns = [
+    path('healthz/', ok_view, name='healthz'),
+    path('raise-403/', deny_view, name='raise_403'),
+    path('raise-500/', explode_view, name='raise_500'),
+    path('', include('workflows.urls')),
+]

backend/workflows/tests/test_error_pages.py

@@ -0,0 +1,62 @@
+from django.test import Client, RequestFactory, TestCase, override_settings
+
+from workflows.error_views import csrf_failure
+
+
+@override_settings(
+    DEBUG=False,
+    ROOT_URLCONF='workflows.tests.error_test_urls',
+    ALLOWED_HOSTS=['testserver'],
+)
+class ErrorPageTests(TestCase):
+    def setUp(self):
+        self.client = Client()
+        self.client.raise_request_exception = False
+
+    def test_custom_404_page_is_rendered(self):
+        response = self.client.get('/missing-page/')
+
+        self.assertEqual(response.status_code, 404)
+        self.assertTemplateUsed(response, 'workflows/errors/error_page.html')
+        self.assertContains(response, '404', status_code=404)
+
+    def test_custom_403_page_is_rendered(self):
+        response = self.client.get('/raise-403/')
+
+        self.assertEqual(response.status_code, 403)
+        self.assertTemplateUsed(response, 'workflows/errors/error_page.html')
+        self.assertContains(response, '403', status_code=403)
+
+    def test_custom_500_page_is_rendered(self):
+        response = self.client.get('/raise-500/')
+
+        self.assertEqual(response.status_code, 500)
+        self.assertTemplateUsed(response, 'workflows/errors/error_page.html')
+        self.assertContains(response, '500', status_code=500)
+
+    def test_csrf_failure_view_uses_custom_400_page(self):
+        request = RequestFactory().post('/test/')
+
+        response = csrf_failure(request)
+
+        self.assertEqual(response.status_code, 400)
+        self.assertContains(response, '400', status_code=400)
+
+
+@override_settings(
+    DEBUG=True,
+    FORCE_BRANDED_ERROR_PAGES=True,
+    ROOT_URLCONF='workflows.tests.error_test_urls',
+    ALLOWED_HOSTS=['testserver'],
+)
+class ForcedBrandedErrorPageTests(TestCase):
+    def setUp(self):
+        self.client = Client()
+        self.client.raise_request_exception = False
+
+    def test_missing_url_uses_branded_404_even_with_debug_enabled(self):
+        response = self.client.get('/missing-page/')
+
+        self.assertEqual(response.status_code, 404)
+        self.assertTemplateUsed(response, 'workflows/errors/error_page.html')
+        self.assertContains(response, '404', status_code=404)