django/tests/handlers/tests_custom_error_handlers.py

from django.core.exceptions import PermissionDenied
from django.template.response import TemplateResponse
from django.test import SimpleTestCase, modify_settings, override_settings
from django.urls import path


class MiddlewareAccessingContent:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        response = self.get_response(request)
        # Response.content should be available in the middleware even with a
        # TemplateResponse-based exception response.
        assert response.content
        return response


def template_response_error_handler(request, exception=None):
    return TemplateResponse(request, 'test_handler.html', status=403)


def permission_denied_view(request):
    raise PermissionDenied


urlpatterns = [
    path('', permission_denied_view),
]

handler403 = template_response_error_handler


@override_settings(ROOT_URLCONF='handlers.tests_custom_error_handlers')
@modify_settings(MIDDLEWARE={'append': 'handlers.tests_custom_error_handlers.MiddlewareAccessingContent'})
class CustomErrorHandlerTests(SimpleTestCase):

    def test_handler_renders_template_response(self):
        """
        BaseHandler should render TemplateResponse if necessary.
        """
        response = self.client.get('/')
        self.assertContains(response, 'Error handler content', status_code=403)