# Django 4.2.11 documentation

# Source code for django.test.testcases

    import difflib
    import inspect
    import json
    import logging
    import posixpath
    import sys
    import threading
    import unittest
    import warnings
    from collections import Counter
    from contextlib import contextmanager
    from copy import copy, deepcopy
    from difflib import get_close_matches
    from functools import wraps
    from unittest.suite import _DebugResult
    from unittest.util import safe_repr
    from urllib.parse import (
        parse_qsl,
        unquote,
        urlencode,
        urljoin,
        urlparse,
        urlsplit,
        urlunparse,
    )
    from urllib.request import url2pathname

    from asgiref.sync import async_to_sync, iscoroutinefunction

    from django.apps import apps
    from django.conf import settings
    from django.core import mail
    from django.core.exceptions import ImproperlyConfigured, ValidationError
    from django.core.files import locks
    from django.core.handlers.wsgi import WSGIHandler, get_path_info
    from django.core.management import call_command
    from django.core.management.color import no_style
    from django.core.management.sql import emit_post_migrate_signal
    from django.core.servers.basehttp import ThreadedWSGIServer, WSGIRequestHandler
    from django.core.signals import setting_changed
    from django.db import DEFAULT_DB_ALIAS, connection, connections, transaction
    from django.forms.fields import CharField
    from django.http import QueryDict
    from django.http.request import split_domain_port, validate_host
    from django.http.response import HttpResponseBase
    from django.test.client import AsyncClient, Client
    from django.test.html import HTMLParseError, parse_html
    from django.test.signals import template_rendered
    from django.test.utils import (
        CaptureQueriesContext,
        ContextList,
        compare_xml,
        modify_settings,
        override_settings,
    )
    from django.utils.deprecation import RemovedInDjango50Warning, RemovedInDjango51Warning
    from django.utils.functional import classproperty
    from django.utils.version import PY310
    from django.views.static import serve

    logger = logging.getLogger("django.test")

    __all__ = (
        "TestCase",
        "TransactionTestCase",
        "SimpleTestCase",
        "skipIfDBFeature",
        "skipUnlessDBFeature",
    )

    def to_list(value):
        """Put value into a list if it's not already one."""
        if not isinstance(value, list):
            value = [value]
        return value

    def assert_and_parse_html(self, html, user_msg, msg):
        try:
            dom = parse_html(html)
        except HTMLParseError as e:
            standardMsg = "%s\n%s" % (msg, e)
            self.fail(self._formatMessage(user_msg, standardMsg))
        return dom

    class _AssertNumQueriesContext(CaptureQueriesContext):
        def __init__(self, test_case, num, connection):
            self.test_case = test_case
            self.num = num
            super().__init__(connection)

        def __exit__(self, exc_type, exc_value, traceback):
            super().__exit__(exc_type, exc_value, traceback)
            if exc_type is not None:
                return
            executed = len(self)
            self.test_case.assertEqual(
                executed,
                self.num,
                "%d queries executed, %d expected\nCaptured queries were:\n%s"
                % (
                    executed,
                    self.num,
                    "\n".join(
                        "%d. %s" % (i, query["sql"])
                        for i, query in enumerate(self.captured_queries, start=1)
                    ),
                ),
            )

    class _AssertTemplateUsedContext:
        def __init__(self, test_case, template_name, msg_prefix="", count=None):
            self.test_case = test_case
            self.template_name = template_name
            self.msg_prefix = msg_prefix
            self.count = count

            self.rendered_templates = []
            self.rendered_template_names = []
            self.context = ContextList()

        def on_template_render(self, sender, signal, template, context, **kwargs):
            self.rendered_templates.append(template)
            self.rendered_template_names.append(template.name)
            self.context.append(copy(context))

        def test(self):
            self.test_case._assert_template_used(
                self.template_name,
                self.rendered_template_names,
                self.msg_prefix,
                self.count,
            )

        def __enter__(self):
            template_rendered.connect(self.on_template_render)
            return self

        def __exit__(self, exc_type, exc_value, traceback):
            template_rendered.disconnect(self.on_template_render)
            if exc_type is not None:
                return
            self.test()

    class _AssertTemplateNotUsedContext(_AssertTemplateUsedContext):
        def test(self):
            self.test_case.assertFalse(
                self.template_name in self.rendered_template_names,
                f"{self.msg_prefix}Template '{self.template_name}' was used "
                f"unexpectedly in rendering the response",
            )

    class DatabaseOperationForbidden(AssertionError):
        pass

    class _DatabaseFailure:
        def __init__(self, wrapped, message):
            self.wrapped = wrapped
            self.message = message

        def __call__(self):
            raise DatabaseOperationForbidden(self.message)

    # RemovedInDjango50Warning
    class _AssertFormErrorDeprecationHelper:
        @staticmethod
        def assertFormError(self, response, form, field, errors, msg_prefix=""):
            """
            Search through all the rendered contexts of the `response` for a form named
            `form` then dispatch to the new assertFormError() using that instance.
            If multiple contexts contain the form, they're all checked in order and any
            failure will abort (this matches the old behavior).
            """
            warning_msg = (
                f"Passing response to assertFormError() is deprecated. Use the form object "
                f"directly: assertFormError(response.context[{form!r}], {field!r}, ...)"
            )
            warnings.warn(warning_msg, RemovedInDjango50Warning, stacklevel=2)

            full_msg_prefix = f"{msg_prefix}: " if msg_prefix else ""
            contexts = to_list(response.context) if response.context is not None else []
            if not contexts:
                self.fail(
                    f"{full_msg_prefix}Response did not use any contexts to render the "
                    f"response"
                )
            # Search all contexts for the error.
            found_form = False
            for i, context in enumerate(contexts):
                if form not in context:
                    continue
                found_form = True
                self.assertFormError(context[form], field, errors, msg_prefix=msg_prefix)
            if not found_form:
                self.fail(
                    f"{full_msg_prefix}The form '{form}' was not used to render the "
                    f"response"
                )

        @staticmethod
        def assertFormSetError(
            self, response, formset, form_index, field, errors, msg_prefix=""
        ):
            """
            Search for a formset named "formset" in the "response" and dispatch to
            the new assertFormSetError() using that instance. If the name is found
            in multiple contexts they're all checked in order and any failure will
            abort the test.
            """
            warning_msg = (
                f"Passing response to assertFormSetError() is deprecated. Use the formset "
                f"object directly: assertFormSetError(response.context[{formset!r}], "
                f"{form_index!r}, ...)"
            )
            warnings.warn(warning_msg, RemovedInDjango50Warning, stacklevel=2)

            full_msg_prefix = f"{msg_prefix}: " if msg_prefix else ""
            contexts = to_list(response.context) if response.context is not None else []
            if not contexts:
                self.fail(
                    f"{full_msg_prefix}Response did not use any contexts to render the "
                    f"response"
                )
            found_formset = False
            for i, context in enumerate(contexts):
                if formset not in context or not hasattr(context[formset], "forms"):
                    continue
                found_formset = True
                self.assertFormSetError(
                    context[formset], form_index, field, errors, msg_prefix
                )
            if not found_formset:
                self.fail(
                    f"{full_msg_prefix}The formset '{formset}' was not used to render the "
                    f"response"
                )

        @classmethod
        def patch_signature(cls, new_method):
            """
            Replace the decorated method with a new one that inspects the passed
            args/kwargs and dispatch to the old implementation (with deprecation
            warning) when it detects the old signature.
            """

            @wraps(new_method)
            def patched_method(self, *args, **kwargs):
                old_method = getattr(cls, new_method.__name__)
                old_signature = inspect.signature(old_method)
                try:
                    old_bound_args = old_signature.bind(self, *args, **kwargs)
                except TypeError:
                    # If old signature doesn't match then either:
                    # 1) new signature will match
                    # 2) or a TypeError will be raised showing the user information
                    # about the new signature.
                    return new_method(self, *args, **kwargs)

                new_signature = inspect.signature(new_method)
                try:
                    new_bound_args = new_signature.bind(self, *args, **kwargs)
                except TypeError:
                    # Old signature matches but not the new one (because of
                    # previous try/except).
                    return old_method(self, *args, **kwargs)

                # If both signatures match, decide on which method to call by
                # inspecting the first arg (arg[0] = self).
                assert old_bound_args.args[1] == new_bound_args.args[1]
                if hasattr(
                    old_bound_args.args[1], "context"
                ):  # Looks like a response object => old method.
                    return old_method(self, *args, **kwargs)
                elif isinstance(old_bound_args.args[1], HttpResponseBase):
                    raise ValueError(
                        f"{old_method.__name__}() is only usable on responses fetched "
                        f"using the Django test Client."
                    )
                else:
                    return new_method(self, *args, **kwargs)

            return patched_method

    class SimpleTestCase(unittest.TestCase):
        # The class we'll use for the test client self.client.
        # Can be overridden in derived classes.
        client_class = Client
        async_client_class = AsyncClient
        _overridden_settings = None
        _modified_settings = None

        databases = set()
        _disallowed_database_msg = (
            "Database %(operation)s to %(alias)r are not allowed in SimpleTestCase "
            "subclasses. Either subclass TestCase or TransactionTestCase to ensure "
            "proper test isolation or add %(alias)r to %(test)s.databases to silence "
            "this failure."
        )
        _disallowed_connection_methods = [
            ("connect", "connections"),
            ("temporary_connection", "connections"),
            ("cursor", "queries"),
            ("chunked_cursor", "queries"),
        ]

        @classmethod
        def setUpClass(cls):
            super().setUpClass()
            if cls._overridden_settings:
                cls._cls_overridden_context = override_settings(**cls._overridden_settings)
                cls._cls_overridden_context.enable()
                cls.addClassCleanup(cls._cls_overridden_context.disable)
            if cls._modified_settings:
                cls._cls_modified_context = modify_settings(cls._modified_settings)
                cls._cls_modified_context.enable()
                cls.addClassCleanup(cls._cls_modified_context.disable)
            cls._add_databases_failures()
            cls.addClassCleanup(cls._remove_databases_failures)

        @classmethod
        def _validate_databases(cls):
            if cls.databases == "__all__":
                return frozenset(connections)
            for alias in cls.databases:
                if alias not in connections:
                    message = (
                        "%s.%s.databases refers to %r which is not defined in "
                        "settings.DATABASES."
                        % (
                            cls.__module__,
                            cls.__qualname__,
                            alias,
                        )
                    )
                    close_matches = get_close_matches(alias, list(connections))
                    if close_matches:
                        message += " Did you mean %r?" % close_matches[0]
                    raise ImproperlyConfigured(message)
            return frozenset(cls.databases)

        @classmethod
        def _add_databases_failures(cls):
            cls.databases = cls._validate_databases()
            for alias in connections:
                if alias in cls.databases:
                    continue
                connection = connections[alias]
                for name, operation in cls._disallowed_connection_methods:
                    message = cls._disallowed_database_msg % {
                        "test": "%s.%s" % (cls.__module__, cls.__qualname__),
                        "alias": alias,
                        "operation": operation,
                    }
                    method = getattr(connection, name)
                    setattr(connection, name, _DatabaseFailure(method, message))

        @classmethod
        def _remove_databases_failures(cls):
            for alias in connections:
                if alias in cls.databases:
                    continue
                connection = connections[alias]
                for name, _ in cls._disallowed_connection_methods:
                    method = getattr(connection, name)
                    setattr(connection, name, method.wrapped)

        def __call__(self, result=None):
            """
            Wrapper around default __call__ method to perform common Django test
            set up. This means that user-defined Test Cases aren't required to
            include a call to super().setUp().
            """
            self._setup_and_call(result)

        def debug(self):
            """Perform the same as __call__(), without catching the exception."""
            debug_result = _DebugResult()
            self._setup_and_call(debug_result, debug=True)

        def _setup_and_call(self, result, debug=False):
            """
            Perform the following in order: pre-setup, run test, post-teardown,
            skipping pre/post hooks if test is set to be skipped.

            If debug=True, reraise any errors in setup and use super().debug()
            instead of __call__() to run the test.
            """
            testMethod = getattr(self, self._testMethodName)
            skipped = getattr(self.__class__, "__unittest_skip__", False) or getattr(
                testMethod, "__unittest_skip__", False
            )

            # Convert async test methods.
            if iscoroutinefunction(testMethod):
                setattr(self, self._testMethodName, async_to_sync(testMethod))

            if not skipped:
                try:
                    self._pre_setup()
                except Exception:
                    if debug:
                        raise
                    result.addError(self, sys.exc_info())
                    return
            if debug:
                super().debug()
            else:
                super().__call__(result)
            if not skipped:
                try:
                    self._post_teardown()
                except Exception:
                    if debug:
                        raise
                    result.addError(self, sys.exc_info())
                    return

        def _pre_setup(self):
            """
            Perform pre-test setup:
            * Create a test client.
            * Clear the mail test outbox.
            """
            self.client = self.client_class()
            self.async_client = self.async_client_class()
            mail.outbox = []

        def _post_teardown(self):
            """Perform post-test things."""
            pass

        def settings(self, **kwargs):
            """
            A context manager that temporarily sets a setting and reverts to the
            original value when exiting the context.
            """
            return override_settings(**kwargs)

        def modify_settings(self, **kwargs):
            """
            A context manager that temporarily applies changes a list setting and
            reverts back to the original value when exiting the context.
            """
            return modify_settings(**kwargs)

        def assertRedirects(
            self,
            response,
            expected_url,
            status_code=302,
            target_status_code=200,
            msg_prefix="",
            fetch_redirect_response=True,
        ):
            """
            Assert that a response redirected to a specific URL and that the
            redirect URL can be loaded.

            Won't work for external links since it uses the test client to do a
            request (use fetch_redirect_response=False to check such links without
            fetching them).
            """
            if msg_prefix:
                msg_prefix += ": "

            if hasattr(response, "redirect_chain"):
                # The request was a followed redirect
                self.assertTrue(
                    response.redirect_chain,
                    msg_prefix
                    + (
                        "Response didn't redirect as expected: Response code was %d "
                        "(expected %d)"
                    )
                    % (response.status_code, status_code),
                )

                self.assertEqual(
                    response.redirect_chain[0][1],
                    status_code,
                    msg_prefix
                    + (
                        "Initial response didn't redirect as expected: Response code was "
                        "%d (expected %d)"
                    )
                    % (response.redirect_chain[0][1], status_code),
                )

                url, status_code = response.redirect_chain[-1]

                self.assertEqual(
                    response.status_code,
                    target_status_code,
                    msg_prefix
                    + (
                        "Response didn't redirect as expected: Final Response code was %d "
                        "(expected %d)"
                    )
                    % (response.status_code, target_status_code),
                )

            else:
                # Not a followed redirect
                self.assertEqual(
                    response.status_code,
                    status_code,
                    msg_prefix
                    + (
                        "Response didn't redirect as expected: Response code was %d "
                        "(expected %d)"
                    )
                    % (response.status_code, status_code),
                )

                url = response.url
                scheme, netloc, path, query, fragment = urlsplit(url)

                # Prepend the request path to handle relative path redirects.
                if not path.startswith("/"):
                    url = urljoin(response.request["PATH_INFO"], url)
                    path = urljoin(response.request["PATH_INFO"], path)

                if fetch_redirect_response:
                    # netloc might be empty, or in cases where Django tests the
                    # HTTP scheme, the convention is for netloc to be 'testserver'.
                    # Trust both as "internal" URLs here.
                    domain, port = split_domain_port(netloc)
                    if domain and not validate_host(domain, settings.ALLOWED_HOSTS):
                        raise ValueError(
                            "The test client is unable to fetch remote URLs (got %s). "
                            "If the host is served by Django, add '%s' to ALLOWED_HOSTS. "
                            "Otherwise, use "
                            "assertRedirects(..., fetch_redirect_response=False)."
                            % (url, domain)
                        )
                    # Get the redirection page, using the same client that was used
                    # to obtain the original response.
                    extra = response.client.extra or {}
                    headers = response.client.headers or {}
                    redirect_response = response.client.get(
                        path,
                        QueryDict(query),
                        secure=(scheme == "https"),
                        headers=headers,
                        **extra,
                    )
                    self.assertEqual(
                        redirect_response.status_code,
                        target_status_code,
                        msg_prefix
                        + (
                            "Couldn't retrieve redirection page '%s': response code was %d "
                            "(expected %d)"
                        )
                        % (path, redirect_response.status_code, target_status_code),
                    )

            self.assertURLEqual(
                url,
                expected_url,
                msg_prefix
                + "Response redirected to '%s', expected '%s'" % (url, expected_url),
            )

        def assertURLEqual(self, url1, url2, msg_prefix=""):
            """
            Assert that two URLs are the same, ignoring the order of query string
            parameters except for parameters with the same name.

            For example, /path/?x=1&y=2 is equal to /path/?y=2&x=1, but
            /path/?a=1&a=2 isn't equal to /path/?a=2&a=1.
            """

            def normalize(url):
                """Sort the URL's query string parameters."""
                url = str(url)  # Coerce reverse_lazy() URLs.
                scheme, netloc, path, params, query, fragment = urlparse(url)
                query_parts = sorted(parse_qsl(query))
                return urlunparse(
                    (scheme, netloc, path, params, urlencode(query_parts), fragment)
                )

            self.assertEqual(
                normalize(url1),
                normalize(url2),
                msg_prefix + "Expected '%s' to equal '%s'." % (url1, url2),
            )

        def _assert_contains(self, response, text, status_code, msg_prefix, html):
            # If the response supports deferred rendering and hasn't been rendered
            # yet, then ensure that it does get rendered before proceeding further.
            if (
                hasattr(response, "render")
                and callable(response.render)
                and not response.is_rendered
            ):
                response.render()

            if msg_prefix:
                msg_prefix += ": "

            self.assertEqual(
                response.status_code,
                status_code,
                msg_prefix + "Couldn't retrieve content: Response code was %d"
                " (expected %d)" % (response.status_code, status_code),
            )

            if response.streaming:
                content = b"".join(response.streaming_content)
            else:
                content = response.content
            if not isinstance(text, bytes) or html:
                text = str(text)
                content = content.decode(response.charset)
                text_repr = "'%s'" % text
            else:
                text_repr = repr(text)
            if html:
                content = assert_and_parse_html(
                    self, content, None, "Response's content is not valid HTML:"
                )
                text = assert_and_parse_html(
                    self, text, None, "Second argument is not valid HTML:"
                )
            real_count = content.count(text)
            return (text_repr, real_count, msg_prefix)

        def assertContains(
            self, response, text, count=None, status_code=200, msg_prefix="", html=False
        ):
            """
            Assert that a response indicates that some content was retrieved
            successfully, (i.e., the HTTP status code was as expected) and that
            ``text`` occurs ``count`` times in the content of the response.
            If ``count`` is None, the count doesn't matter - the assertion is true
            if the text occurs at least once in the response.
            """
            text_repr, real_count, msg_prefix = self._assert_contains(
                response, text, status_code, msg_prefix, html
            )

            if count is not None:
                self.assertEqual(
                    real_count,
                    count,
                    msg_prefix
                    + "Found %d instances of %s in response (expected %d)"
                    % (real_count, text_repr, count),
                )
            else:
                self.assertTrue(
                    real_count != 0, msg_prefix + "Couldn't find %s in response" % text_repr
                )

        def assertNotContains(
            self, response, text, status_code=200, msg_prefix="", html=False
        ):
            """
            Assert that a response indicates that some content was retrieved
            successfully, (i.e., the HTTP status code was as expected) and that
            ``text`` doesn't occur in the content of the response.
            """
            text_repr, real_count, msg_prefix = self._assert_contains(
                response, text, status_code, msg_prefix, html
            )

            self.assertEqual(
                real_count, 0, msg_prefix + "Response should not contain %s" % text_repr
            )

        def _check_test_client_response(self, response, attribute, method_name):
            """
            Raise a ValueError if the given response doesn't have the required
            attribute.
            """
            if not hasattr(response, attribute):
                raise ValueError(
                    f"{method_name}() is only usable on responses fetched using "
                    "the Django test Client."
                )

        def _assert_form_error(self, form, field, errors, msg_prefix, form_repr):
            if not form.is_bound:
                self.fail(
                    f"{msg_prefix}The {form_repr} is not bound, it will never have any "
                    f"errors."
                )

            if field is not None and field not in form.fields:
                self.fail(
                    f"{msg_prefix}The {form_repr} does not contain the field {field!r}."
                )
            if field is None:
                field_errors = form.non_field_errors()
                failure_message = f"The non-field errors of {form_repr} don't match."
            else:
                field_errors = form.errors.get(field, [])
                failure_message = (
                    f"The errors of field {field!r} on {form_repr} don't match."
                )

            self.assertEqual(field_errors, errors, msg_prefix + failure_message)

        # RemovedInDjango50Warning: When the deprecation ends, remove the
        # decorator.

        @_AssertFormErrorDeprecationHelper.patch_signature
        def assertFormError(self, form, field, errors, msg_prefix=""):
            """
            Assert that a field named "field" on the given form object has specific
            errors.

            errors can be either a single error message or a list of errors
            messages. Using errors=[] test that the field has no errors.

            You can pass field=None to check the form's non-field errors.
            """
            if errors is None:
                warnings.warn(
                    "Passing errors=None to assertFormError() is deprecated, use "
                    "errors=[] instead.",
                    RemovedInDjango50Warning,
                    stacklevel=2,
                )
                errors = []

            if msg_prefix:
                msg_prefix += ": "
            errors = to_list(errors)
            self._assert_form_error(form, field, errors, msg_prefix, f"form {form!r}")

        # RemovedInDjango51Warning.
        def assertFormsetError(self, *args, **kw):
            warnings.warn(
                "assertFormsetError() is deprecated in favor of assertFormSetError().",
                category=RemovedInDjango51Warning,
                stacklevel=2,
            )
            return self.assertFormSetError(*args, **kw)

        # RemovedInDjango50Warning: When the deprecation ends, remove the
        # decorator.

        @_AssertFormErrorDeprecationHelper.patch_signature
        def assertFormSetError(self, formset, form_index, field, errors, msg_prefix=""):
            """
            Similar to assertFormError() but for formsets.

            Use form_index=None to check the formset's non-form errors (in that
            case, you must also use field=None).
            Otherwise use an integer to check the formset's n-th form for errors.

            Other parameters are the same as assertFormError().
            """
            if errors is None:
                warnings.warn(
                    "Passing errors=None to assertFormSetError() is deprecated, "
                    "use errors=[] instead.",
                    RemovedInDjango50Warning,
                    stacklevel=2,
                )
                errors = []

            if form_index is None and field is not None:
                raise ValueError("You must use field=None with form_index=None.")

            if msg_prefix:
                msg_prefix += ": "
            errors = to_list(errors)

            if not formset.is_bound:
                self.fail(
                    f"{msg_prefix}The formset {formset!r} is not bound, it will never have "
                    f"any errors."
                )
            if form_index is not None and form_index >= formset.total_form_count():
                form_count = formset.total_form_count()
                form_or_forms = "forms" if form_count > 1 else "form"
                self.fail(
                    f"{msg_prefix}The formset {formset!r} only has {form_count} "
                    f"{form_or_forms}."
                )
            if form_index is not None:
                form_repr = f"form {form_index} of formset {formset!r}"
                self._assert_form_error(
                    formset.forms[form_index], field, errors, msg_prefix, form_repr
                )
            else:
                failure_message = f"The non-form errors of formset {formset!r} don't match."
                self.assertEqual(
                    formset.non_form_errors(), errors, msg_prefix + failure_message
                )

        def _get_template_used(self, response, template_name, msg_prefix, method_name):
            if response is None and template_name is None:
                raise TypeError("response and/or template_name argument must be provided")

            if msg_prefix:
                msg_prefix += ": "

            if template_name is not None and response is not None:
                self._check_test_client_response(response, "templates", method_name)

            if not hasattr(response, "templates") or (response is None and template_name):
                if response:
                    template_name = response
                    response = None
                # use this template with context manager
                return template_name, None, msg_prefix

            template_names = [t.name for t in response.templates if t.name is not None]
            return None, template_names, msg_prefix

        def _assert_template_used(self, template_name, template_names, msg_prefix, count):
            if not template_names:
                self.fail(msg_prefix + "No templates used to render the response")
            self.assertTrue(
                template_name in template_names,
                msg_prefix + "Template '%s' was not a template used to render"
                " the response. Actual template(s) used: %s"
                % (template_name, ", ".join(template_names)),
            )

            if count is not None:
                self.assertEqual(
                    template_names.count(template_name),
                    count,
                    msg_prefix + "Template '%s' was expected to be rendered %d "
                    "time(s) but was actually rendered %d time(s)."
                    % (template_name, count, template_names.count(template_name)),
                )

        def assertTemplateUsed(
            self, response=None, template_name=None, msg_prefix="", count=None
        ):
            """
            Assert that the template with the provided name was used in rendering
            the response. Also usable as context manager.
            """
            context_mgr_template, template_names, msg_prefix = self._get_template_used(
                response,
                template_name,
                msg_prefix,
                "assertTemplateUsed",
            )
            if context_mgr_template:
                # Use assertTemplateUsed as context manager.
                return _AssertTemplateUsedContext(
                    self, context_mgr_template, msg_prefix, count
                )

            self._assert_template_used(template_name, template_names, msg_prefix, count)

        def assertTemplateNotUsed(self, response=None, template_name=None, msg_prefix=""):
            """
            Assert that the template with the provided name was NOT used in
            rendering the response. Also usable as context manager.
            """
            context_mgr_template, template_names, msg_prefix = self._get_template_used(
                response,
                template_name,
                msg_prefix,
                "assertTemplateNotUsed",
            )
            if context_mgr_template:
                # Use assertTemplateNotUsed as context manager.
                return _AssertTemplateNotUsedContext(self, context_mgr_template, msg_prefix)

            self.assertFalse(
                template_name in template_names,
                msg_prefix
                + "Template '%s' was used unexpectedly in rendering the response"
                % template_name,
            )

        @contextmanager
        def _assert_raises_or_warns_cm(
            self, func, cm_attr, expected_exception, expected_message
        ):
            with func(expected_exception) as cm:
                yield cm
            self.assertIn(expected_message, str(getattr(cm, cm_attr)))

        def _assertFooMessage(
            self, func, cm_attr, expected_exception, expected_message, *args, **kwargs
        ):
            callable_obj = None
            if args:
                callable_obj, *args = args
            cm = self._assert_raises_or_warns_cm(
                func, cm_attr, expected_exception, expected_message
            )
            # Assertion used in context manager fashion.
            if callable_obj is None:
                return cm
            # Assertion was passed a callable.
            with cm:
                callable_obj(*args, **kwargs)

        def assertRaisesMessage(
            self, expected_exception, expected_message, *args, **kwargs
        ):
            """
            Assert that expected_message is found in the message of a raised
            exception.

            Args:
                expected_exception: Exception class expected to be raised.
                expected_message: expected error message string value.
                args: Function to be called and extra positional args.
                kwargs: Extra kwargs.
            """
            return self._assertFooMessage(
                self.assertRaises,
                "exception",
                expected_exception,
                expected_message,
                *args,
                **kwargs,
            )

        def assertWarnsMessage(self, expected_warning, expected_message, *args, **kwargs):
            """
            Same as assertRaisesMessage but for assertWarns() instead of
            assertRaises().
            """
            return self._assertFooMessage(
                self.assertWarns,
                "warning",
                expected_warning,
                expected_message,
                *args,
                **kwargs,
            )

        # A similar method is available in Python 3.10+.
        if not PY310:

            @contextmanager
            def assertNoLogs(self, logger, level=None):
                """
                Assert no messages are logged on the logger, with at least the
                given level.
                """
                if isinstance(level, int):
                    level = logging.getLevelName(level)
                elif level is None:
                    level = "INFO"
                try:
                    with self.assertLogs(logger, level) as cm:
                        yield
                except AssertionError as e:
                    msg = e.args[0]
                    expected_msg = (
                        f"no logs of level {level} or higher triggered on {logger}"
                    )
                    if msg != expected_msg:
                        raise e
                else:
                    self.fail(f"Unexpected logs found: {cm.output!r}")

        def assertFieldOutput(
            self,
            fieldclass,
            valid,
            invalid,
            field_args=None,
            field_kwargs=None,
            empty_value="",
        ):
            """
            Assert that a form field behaves correctly with various inputs.

            Args:
                fieldclass: the class of the field to be tested.
                valid: a dictionary mapping valid inputs to their expected
                        cleaned values.
                invalid: a dictionary mapping invalid inputs to one or more
                        raised error messages.
                field_args: the args passed to instantiate the field
                field_kwargs: the kwargs passed to instantiate the field
                empty_value: the expected clean output for inputs in empty_values
            """
            if field_args is None:
                field_args = []
            if field_kwargs is None:
                field_kwargs = {}
            required = fieldclass(*field_args, **field_kwargs)
            optional = fieldclass(*field_args, **{**field_kwargs, "required": False})
            # test valid inputs
            for input, output in valid.items():
                self.assertEqual(required.clean(input), output)
                self.assertEqual(optional.clean(input), output)
            # test invalid inputs
            for input, errors in invalid.items():
                with self.assertRaises(ValidationError) as context_manager:
                    required.clean(input)
                self.assertEqual(context_manager.exception.messages, errors)

                with self.assertRaises(ValidationError) as context_manager:
                    optional.clean(input)
                self.assertEqual(context_manager.exception.messages, errors)
            # test required inputs
            error_required = [required.error_messages["required"]]
            for e in required.empty_values:
                with self.assertRaises(ValidationError) as context_manager:
                    required.clean(e)
                self.assertEqual(context_manager.exception.messages, error_required)
                self.assertEqual(optional.clean(e), empty_value)
            # test that max_length and min_length are always accepted
            if issubclass(fieldclass, CharField):
                field_kwargs.update({"min_length": 2, "max_length": 20})
                self.assertIsInstance(fieldclass(*field_args, **field_kwargs), fieldclass)

        def assertHTMLEqual(self, html1, html2, msg=None):
            """
            Assert that two HTML snippets are semantically the same.
            Whitespace in most cases is ignored, and attribute ordering is not
            significant. The arguments must be valid HTML.
            """
            dom1 = assert_and_parse_html(
                self, html1, msg, "First argument is not valid HTML:"
            )
            dom2 = assert_and_parse_html(
                self, html2, msg, "Second argument is not valid HTML:"
            )

            if dom1 != dom2:
                standardMsg = "%s != %s" % (safe_repr(dom1, True), safe_repr(dom2, True))
                diff = "\n" + "\n".join(
                    difflib.ndiff(
                        str(dom1).splitlines(),
                        str(dom2).splitlines(),
                    )
                )
                standardMsg = self._truncateMessage(standardMsg, diff)
                self.fail(self._formatMessage(msg, standardMsg))

        def assertHTMLNotEqual(self, html1, html2, msg=None):
            """Assert that two HTML snippets are not semantically equivalent."""
            dom1 = assert_and_parse_html(
                self, html1, msg, "First argument is not valid HTML:"
            )
            dom2 = assert_and_parse_html(
                self, html2, msg, "Second argument is not valid HTML:"
            )

            if dom1 == dom2:
                standardMsg = "%s == %s" % (safe_repr(dom1, True), safe_repr(dom2, True))
                self.fail(self._formatMessage(msg, standardMsg))

        def assertInHTML(self, needle, haystack, count=None, msg_prefix=""):
            needle = assert_and_parse_html(
                self, needle, None, "First argument is not valid HTML:"
            )
            haystack = assert_and_parse_html(
                self, haystack, None, "Second argument is not valid HTML:"
            )
            real_count = haystack.count(needle)
            if count is not None:
                self.assertEqual(
                    real_count,
                    count,
                    msg_prefix
                    + "Found %d instances of '%s' in response (expected %d)"
                    % (real_count, needle, count),
                )
            else:
                self.assertTrue(
                    real_count != 0, msg_prefix + "Couldn't find '%s' in response" % needle
                )

        def assertJSONEqual(self, raw, expected_data, msg=None):
            """
            Assert that the JSON fragments raw and expected_data are equal.
            Usual JSON non-significant whitespace rules apply as the heavyweight
            is delegated to the json library.
            """
            try:
                data = json.loads(raw)
            except json.JSONDecodeError:
                self.fail("First argument is not valid JSON: %r" % raw)
            if isinstance(expected_data, str):
                try:
                    expected_data = json.loads(expected_data)
                except ValueError:
                    self.fail("Second argument is not valid JSON: %r" % expected_data)
            self.assertEqual(data, expected_data, msg=msg)

        def assertJSONNotEqual(self, raw, expected_data, msg=None):
            """
            Assert that the JSON fragments raw and expected_data are not equal.
            Usual JSON non-significant whitespace rules apply as the heavyweight
            is delegated to the json library.
            """
            try:
                data = json.loads(raw)
            except json.JSONDecodeError:
                self.fail("First argument is not valid JSON: %r" % raw)
            if isinstance(expected_data, str):
                try:
                    expected_data = json.loads(expected_data)
                except json.JSONDecodeError:
                    self.fail("Second argument is not valid JSON: %r" % expected_data)
            self.assertNotEqual(data, expected_data, msg=msg)

        def assertXMLEqual(self, xml1, xml2, msg=None):
            """
            Assert that two XML snippets are semantically the same.
            Whitespace in most cases is ignored and attribute ordering is not
            significant. The arguments must be valid XML.
            """
            try:
                result = compare_xml(xml1, xml2)
            except Exception as e:
                standardMsg = "First or second argument is not valid XML\n%s" % e
                self.fail(self._formatMessage(msg, standardMsg))
            else:
                if not result:
                    standardMsg = "%s != %s" % (
                        safe_repr(xml1, True),
                        safe_repr(xml2, True),
                    )
                    diff = "\n" + "\n".join(
                        difflib.ndiff(xml1.splitlines(), xml2.splitlines())
                    )
                    standardMsg = self._truncateMessage(standardMsg, diff)
                    self.fail(self._formatMessage(msg, standardMsg))

        def assertXMLNotEqual(self, xml1, xml2, msg=None):
            """
            Assert that two XML snippets are not semantically equivalent.
            Whitespace in most cases is ignored and attribute ordering is not
            significant. The arguments must be valid XML.
            """
            try:
                result = compare_xml(xml1, xml2)
            except Exception as e:
                standardMsg = "First or second argument is not valid XML\n%s" % e
                self.fail(self._formatMessage(msg, standardMsg))
            else:
                if result:
                    standardMsg = "%s == %s" % (
                        safe_repr(xml1, True),
                        safe_repr(xml2, True),
                    )
                    self.fail(self._formatMessage(msg, standardMsg))

    class TransactionTestCase(SimpleTestCase):
        # Subclasses can ask for resetting of auto increment sequence before each
        # test case
        reset_sequences = False

        # Subclasses can enable only a subset of apps for faster tests
        available_apps = None

        # Subclasses can define fixtures which will be automatically installed.
        fixtures = None

        databases = {DEFAULT_DB_ALIAS}
        _disallowed_database_msg = (
            "Database %(operation)s to %(alias)r are not allowed in this test. "
            "Add %(alias)r to %(test)s.databases to ensure proper test isolation "
            "and silence this failure."
        )

        # If transactions aren't available, Django will serialize the database
        # contents into a fixture during setup and flush and reload them
        # during teardown (as flush does not restore data from migrations).
        # This can be slow; this flag allows enabling on a per-case basis.
        serialized_rollback = False

        def _pre_setup(self):
            """
            Perform pre-test setup:
            * If the class has an 'available_apps' attribute, restrict the app
              registry to these applications, then fire the post_migrate signal --
              it must run with the correct set of applications for the test case.
            * If the class has a 'fixtures' attribute, install those fixtures.
            """
            super()._pre_setup()
            if self.available_apps is not None:
                apps.set_available_apps(self.available_apps)
                setting_changed.send(
                    sender=settings._wrapped.__class__,
                    setting="INSTALLED_APPS",
                    value=self.available_apps,
                    enter=True,
                )
                for db_name in self._databases_names(include_mirrors=False):
                    emit_post_migrate_signal(verbosity=0, interactive=False, db=db_name)
            try:
                self._fixture_setup()
            except Exception:
                if self.available_apps is not None:
                    apps.unset_available_apps()
                    setting_changed.send(
                        sender=settings._wrapped.__class__,
                        setting="INSTALLED_APPS",
                        value=settings.INSTALLED_APPS,
                        enter=False,
                    )
                raise
            # Clear the queries_log so that it's less likely to overflow (a single
            # test probably won't execute 9K queries). If queries_log overflows,
            # then assertNumQueries() doesn't work.
            for db_name in self._databases_names(include_mirrors=False):
                connections[db_name].queries_log.clear()

        @classmethod
        def _databases_names(cls, include_mirrors=True):
            # Only consider allowed database aliases, including mirrors or not.
            return [
                alias
                for alias in connections
                if alias in cls.databases
                and (
                    include_mirrors
                    or not connections[alias].settings_dict["TEST"]["MIRROR"]
                )
            ]

        def _reset_sequences(self, db_name):
            conn = connections[db_name]
            if conn.features.supports_sequence_reset:
                sql_list = conn.ops.sequence_reset_by_name_sql(
                    no_style(), conn.introspection.sequence_list()
                )
                if sql_list:
                    with transaction.atomic(using=db_name):
                        with conn.cursor() as cursor:
                            for sql in sql_list:
                                cursor.execute(sql)

        def _fixture_setup(self):
            for db_name in self._databases_names(include_mirrors=False):
                # Reset sequences
                if self.reset_sequences:
                    self._reset_sequences(db_name)

                # Provide replica initial data from migrated apps, if needed.
                if self.serialized_rollback and hasattr(
                    connections[db_name], "_test_serialized_contents"
                ):
                    if self.available_apps is not None:
                        apps.unset_available_apps()
                    connections[db_name].creation.deserialize_db_from_string(
                        connections[db_name]._test_serialized_contents
                    )
                    if self.available_apps is not None:
                        apps.set_available_apps(self.available_apps)

                if self.fixtures:
                    # We have to use this slightly awkward syntax due to the fact
                    # that we're using *args and **kwargs together.
                    call_command(
                        "loaddata", *self.fixtures, **{"verbosity": 0, "database": db_name}
                    )

        def _should_reload_connections(self):
            return True

        def _post_teardown(self):
            """
            Perform post-test things:
            * Flush the contents of the database to leave a clean slate. If the
              class has an 'available_apps' attribute, don't fire post_migrate.
            * Force-close the connection so the next test gets a clean cursor.
            """
            try:
                self._fixture_teardown()
                super()._post_teardown()
                if self._should_reload_connections():
                    # Some DB cursors include SQL statements as part of cursor
                    # creation. If you have a test that does a rollback, the effect
                    # of these statements is lost, which can affect the operation of
                    # tests (e.g., losing a timezone setting causing objects to be
                    # created with the wrong time). To make sure this doesn't
                    # happen, get a clean connection at the start of every test.
                    for conn in connections.all(initialized_only=True):
                        conn.close()
            finally:
                if self.available_apps is not None:
                    apps.unset_available_apps()
                    setting_changed.send(
                        sender=settings._wrapped.__class__,
                        setting="INSTALLED_APPS",
                        value=settings.INSTALLED_APPS,
                        enter=False,
                    )

        def _fixture_teardown(self):
            # Allow TRUNCATE ... CASCADE and don't emit the post_migrate signal
            # when flushing only a subset of the apps
            for db_name in self._databases_names(include_mirrors=False):
                # Flush the database
                inhibit_post_migrate = (
                    self.available_apps is not None
                    or (  # Inhibit the post_migrate signal when using serialized
                        # rollback to avoid trying to recreate the serialized data.
                        self.serialized_rollback
                        and hasattr(connections[db_name], "_test_serialized_contents")
                    )
                )
                call_command(
                    "flush",
                    verbosity=0,
                    interactive=False,
                    database=db_name,
                    reset_sequences=False,
                    allow_cascade=self.available_apps is not None,
                    inhibit_post_migrate=inhibit_post_migrate,
                )

        # RemovedInDjango51Warning.
        def assertQuerysetEqual(self, *args, **kw):
            warnings.warn(
                "assertQuerysetEqual() is deprecated in favor of assertQuerySetEqual().",
                category=RemovedInDjango51Warning,
                stacklevel=2,
            )
            return self.assertQuerySetEqual(*args, **kw)

        def assertQuerySetEqual(self, qs, values, transform=None, ordered=True, msg=None):
            values = list(values)
            items = qs
            if transform is not None:
                items = map(transform, items)
            if not ordered:
                return self.assertDictEqual(Counter(items), Counter(values), msg=msg)
            # For example qs.iterator() could be passed as qs, but it does not
            # have 'ordered' attribute.
            if len(values) > 1 and hasattr(qs, "ordered") and not qs.ordered:
                raise ValueError(
                    "Trying to compare non-ordered queryset against more than one "
                    "ordered value."
                )
            return self.assertEqual(list(items), values, msg=msg)

        def assertNumQueries(self, num, func=None, *args, using=DEFAULT_DB_ALIAS, **kwargs):
            conn = connections[using]

            context = _AssertNumQueriesContext(self, num, conn)
            if func is None:
                return context

            with context:
                func(*args, **kwargs)

    def connections_support_transactions(aliases=None):
        """
        Return whether or not all (or specified) connections support
        transactions.
        """
        conns = (
            connections.all()
            if aliases is None
            else (connections[alias] for alias in aliases)
        )
        return all(conn.features.supports_transactions for conn in conns)

    class TestData:
        """
        Descriptor to provide TestCase instance isolation for attributes assigned
        during the setUpTestData() phase.

        Allow safe alteration of objects assigned in setUpTestData() by test
        methods by exposing deep copies instead of the original objects.

        Objects are deep copied using a memo kept on the test case instance in
        order to maintain their original relationships.
        """

        memo_attr = "_testdata_memo"

        def __init__(self, name, data):
            self.name = name
            self.data = data

        def get_memo(self, testcase):
            try:
                memo = getattr(testcase, self.memo_attr)
            except AttributeError:
                memo = {}
                setattr(testcase, self.memo_attr, memo)
            return memo

        def __get__(self, instance, owner):
            if instance is None:
                return self.data
            memo = self.get_memo(instance)
            data = deepcopy(self.data, memo)
            setattr(instance, self.name, data)
            return data

        def __repr__(self):
            return "<TestData: name=%r, data=%r>" % (self.name, self.data)

    class TestCase(TransactionTestCase):
        """
        Similar to TransactionTestCase, but use `transaction.atomic()` to achieve
        test isolation.

        In most situations, TestCase should be preferred to TransactionTestCase as
        it allows faster execution. However, there are some situations where using
        TransactionTestCase might be necessary (e.g. testing some transactional
        behavior).

        On database backends with no transaction support, TestCase behaves as
        TransactionTestCase.
        """

        @classmethod
        def _enter_atomics(cls):
            """Open atomic blocks for multiple databases."""
            atomics = {}
            for db_name in cls._databases_names():
                atomic = transaction.atomic(using=db_name)
                atomic._from_testcase = True
                atomic.__enter__()
                atomics[db_name] = atomic
            return atomics

        @classmethod
        def _rollback_atomics(cls, atomics):
            """Rollback atomic blocks opened by the previous method."""
            for db_name in reversed(cls._databases_names()):
                transaction.set_rollback(True, using=db_name)
                atomics[db_name].__exit__(None, None, None)

        @classmethod
        def _databases_support_transactions(cls):
            return connections_support_transactions(cls.databases)

        @classmethod
        def setUpClass(cls):
            super().setUpClass()
            if not cls._databases_support_transactions():
                return
            cls.cls_atomics = cls._enter_atomics()

            if cls.fixtures:
                for db_name in cls._databases_names(include_mirrors=False):
                    try:
                        call_command(
                            "loaddata",
                            *cls.fixtures,
                            **{"verbosity": 0, "database": db_name},
                        )
                    except Exception:
                        cls._rollback_atomics(cls.cls_atomics)
                        raise
            pre_attrs = cls.__dict__.copy()
            try:
                cls.setUpTestData()
            except Exception:
                cls._rollback_atomics(cls.cls_atomics)
                raise
            for name, value in cls.__dict__.items():
                if value is not pre_attrs.get(name):
                    setattr(cls, name, TestData(name, value))

        @classmethod
        def tearDownClass(cls):
            if cls._databases_support_transactions():
                cls._rollback_atomics(cls.cls_atomics)
                for conn in connections.all(initialized_only=True):
                    conn.close()
            super().tearDownClass()

        @classmethod
        def setUpTestData(cls):
            """Load initial data for the TestCase."""
            pass

        def _should_reload_connections(self):
            if self._databases_support_transactions():
                return False
            return super()._should_reload_connections()

        def _fixture_setup(self):
            if not self._databases_support_transactions():
                # If the backend does not support transactions, we should reload
                # class data before each test
                self.setUpTestData()
                return super()._fixture_setup()

            if self.reset_sequences:
                raise TypeError("reset_sequences cannot be used on TestCase instances")
            self.atomics = self._enter_atomics()

        def _fixture_teardown(self):
            if not self._databases_support_transactions():
                return super()._fixture_teardown()
            try:
                for db_name in reversed(self._databases_names()):
                    if self._should_check_constraints(connections[db_name]):
                        connections[db_name].check_constraints()
            finally:
                self._rollback_atomics(self.atomics)

        def _should_check_constraints(self, connection):
            return (
                connection.features.can_defer_constraint_checks
                and not connection.needs_rollback
                and connection.is_usable()
            )

        @classmethod
        @contextmanager
        def captureOnCommitCallbacks(cls, *, using=DEFAULT_DB_ALIAS, execute=False):
            """Context manager to capture transaction.on_commit() callbacks."""
            callbacks = []
            start_count = len(connections[using].run_on_commit)
            try:
                yield callbacks
            finally:
                while True:
                    callback_count = len(connections[using].run_on_commit)
                    for _, callback, robust in connections[using].run_on_commit[
                        start_count:
                    ]:
                        callbacks.append(callback)
                        if execute:
                            if robust:
                                try:
                                    callback()
                                except Exception as e:
                                    logger.error(
                                        f"Error calling {callback.__qualname__} in "
                                        f"on_commit() (%s).",
                                        e,
                                        exc_info=True,
                                    )
                            else:
                                callback()

                    if callback_count == len(connections[using].run_on_commit):
                        break
                    start_count = callback_count

    class CheckCondition:
        """Descriptor class for deferred condition checking."""

        def __init__(self, *conditions):
            self.conditions = conditions

        def add_condition(self, condition, reason):
            return self.__class__(*self.conditions, (condition, reason))

        def __get__(self, instance, cls=None):
            # Trigger access for all bases.
            if any(getattr(base, "__unittest_skip__", False) for base in cls.__bases__):
                return True
            for condition, reason in self.conditions:
                if condition():
                    # Override this descriptor's value and set the skip reason.
                    cls.__unittest_skip__ = True
                    cls.__unittest_skip_why__ = reason
                    return True
            return False

    def _deferredSkip(condition, reason, name):
        def decorator(test_func):
            nonlocal condition
            if not (
                isinstance(test_func, type) and issubclass(test_func, unittest.TestCase)
            ):

                @wraps(test_func)
                def skip_wrapper(*args, **kwargs):
                    if (
                        args
                        and isinstance(args[0], unittest.TestCase)
                        and connection.alias not in getattr(args[0], "databases", {})
                    ):
                        raise ValueError(
                            "%s cannot be used on %s as %s doesn't allow queries "
                            "against the %r database."
                            % (
                                name,
                                args[0],
                                args[0].__class__.__qualname__,
                                connection.alias,
                            )
                        )
                    if condition():
                        raise unittest.SkipTest(reason)
                    return test_func(*args, **kwargs)

                test_item = skip_wrapper
            else:
                # Assume a class is decorated
                test_item = test_func
                databases = getattr(test_item, "databases", None)
                if not databases or connection.alias not in databases:
                    # Defer raising to allow importing test class's module.
                    def condition():
                        raise ValueError(
                            "%s cannot be used on %s as it doesn't allow queries "
                            "against the '%s' database."
                            % (
                                name,
                                test_item,
                                connection.alias,
                            )
                        )

                # Retrieve the possibly existing value from the class's dict to
                # avoid triggering the descriptor.
                skip = test_func.__dict__.get("__unittest_skip__")
                if isinstance(skip, CheckCondition):
                    test_item.__unittest_skip__ = skip.add_condition(condition, reason)
                elif skip is not True:
                    test_item.__unittest_skip__ = CheckCondition((condition, reason))
            return test_item

        return decorator

    def skipIfDBFeature(*features):
        """Skip a test if a database has at least one of the named features."""
        return _deferredSkip(
            lambda: any(
                getattr(connection.features, feature, False) for feature in features
            ),
            "Database has feature(s) %s" % ", ".join(features),
            "skipIfDBFeature",
        )

    def skipUnlessDBFeature(*features):
        """Skip a test unless a database has all the named features."""
        return _deferredSkip(
            lambda: not all(
                getattr(connection.features, feature, False) for feature in features
            ),
            "Database doesn't support feature(s): %s" % ", ".join(features),
            "skipUnlessDBFeature",
        )

    def skipUnlessAnyDBFeature(*features):
        """Skip a test unless a database has any of the named features."""
        return _deferredSkip(
            lambda: not any(
                getattr(connection.features, feature, False) for feature in features
            ),
            "Database doesn't support any of the feature(s): %s" % ", ".join(features),
            "skipUnlessAnyDBFeature",
        )

    class QuietWSGIRequestHandler(WSGIRequestHandler):
        """
        A WSGIRequestHandler that doesn't log to standard output any of the
        requests received, so as to not clutter the test result output.
        """

        def log_message(*args):
            pass

    class FSFilesHandler(WSGIHandler):
        """
        WSGI middleware that intercepts calls to a directory, as defined by one of
        the *_ROOT settings, and serves those files, publishing them under *_URL.
        """

        def __init__(self, application):
            self.application = application
            self.base_url = urlparse(self.get_base_url())
            super().__init__()

        def _should_handle(self, path):
            """
            Check if the path should be handled. Ignore the path if:
            * the host is provided as part of the base_url
            * the request's path isn't under the media path (or equal)
            """
            return path.startswith(self.base_url[2]) and not self.base_url[1]

        def file_path(self, url):
            """Return the relative path to the file on disk for the given URL."""
            relative_url = url[len(self.base_url[2]) :]
            return url2pathname(relative_url)

        def get_response(self, request):
            from django.http import Http404

            if self._should_handle(request.path):
                try:
                    return self.serve(request)
                except Http404:
                    pass
            return super().get_response(request)

        def serve(self, request):
            os_rel_path = self.file_path(request.path)
            os_rel_path = posixpath.normpath(unquote(os_rel_path))
            # Emulate behavior of django.contrib.staticfiles.views.serve() when it
            # invokes staticfiles' finders functionality.
            # TODO: Modify if/when that internal API is refactored
            final_rel_path = os_rel_path.replace("\\", "/").lstrip("/")
            return serve(request, final_rel_path, document_root=self.get_base_dir())

        def __call__(self, environ, start_response):
            if not self._should_handle(get_path_info(environ)):
                return self.application(environ, start_response)
            return super().__call__(environ, start_response)

    class _StaticFilesHandler(FSFilesHandler):
        """
        Handler for serving static files. A private class that is meant to be used
        solely as a convenience by LiveServerThread.
        """

        def get_base_dir(self):
            return settings.STATIC_ROOT

        def get_base_url(self):
            return settings.STATIC_URL

    class _MediaFilesHandler(FSFilesHandler):
        """
        Handler for serving the media files. A private class that is meant to be
        used solely as a convenience by LiveServerThread.
        """

        def get_base_dir(self):
            return settings.MEDIA_ROOT

        def get_base_url(self):
            return settings.MEDIA_URL

    class LiveServerThread(threading.Thread):
        """Thread for running a live HTTP server while the tests are running."""

        server_class = ThreadedWSGIServer

        def __init__(self, host, static_handler, connections_override=None, port=0):
            self.host = host
            self.port = port
            self.is_ready = threading.Event()
            self.error = None
            self.static_handler = static_handler
            self.connections_override = connections_override
            super().__init__()

        def run(self):
            """
            Set up the live server and databases, and then loop over handling
            HTTP requests.
            """
            if self.connections_override:
                # Override this thread's database connections with the ones
                # provided by the main thread.
                for alias, conn in self.connections_override.items():
                    connections[alias] = conn
            try:
                # Create the handler for serving static and media files
                handler = self.static_handler(_MediaFilesHandler(WSGIHandler()))
                self.httpd = self._create_server(
                    connections_override=self.connections_override,
                )
                # If binding to port zero, assign the port allocated by the OS.
                if self.port == 0:
                    self.port = self.httpd.server_address[1]
                self.httpd.set_app(handler)
                self.is_ready.set()
                self.httpd.serve_forever()
            except Exception as e:
                self.error = e
                self.is_ready.set()
            finally:
                connections.close_all()

        def _create_server(self, connections_override=None):
            return self.server_class(
                (self.host, self.port),
                QuietWSGIRequestHandler,
                allow_reuse_address=False,
                connections_override=connections_override,
            )

        def terminate(self):
            if hasattr(self, "httpd"):
                # Stop the WSGI server
                self.httpd.shutdown()
                self.httpd.server_close()
            self.join()

    class LiveServerTestCase(TransactionTestCase):
        """
        Do basically the same as TransactionTestCase but also launch a live HTTP
        server in a separate thread so that the tests may use another testing
        framework, such as Selenium for example, instead of the built-in dummy
        client.
        It inherits from TransactionTestCase instead of TestCase because the
        threads don't share the same transactions (unless if using in-memory sqlite)
        and each thread needs to commit all their transactions so that the other
        thread can see the changes.
        """

        host = "localhost"
        port = 0
        server_thread_class = LiveServerThread
        static_handler = _StaticFilesHandler

        @classproperty
        def live_server_url(cls):
            return "http://%s:%s" % (cls.host, cls.server_thread.port)

        @classproperty
        def allowed_host(cls):
            return cls.host

        @classmethod
        def _make_connections_override(cls):
            connections_override = {}
            for conn in connections.all():
                # If using in-memory sqlite databases, pass the connections to
                # the server thread.
                if conn.vendor == "sqlite" and conn.is_in_memory_db():
                    connections_override[conn.alias] = conn
            return connections_override

        @classmethod
        def setUpClass(cls):
            super().setUpClass()
            cls._live_server_modified_settings = modify_settings(
                ALLOWED_HOSTS={"append": cls.allowed_host},
            )
            cls._live_server_modified_settings.enable()
            cls.addClassCleanup(cls._live_server_modified_settings.disable)
            cls._start_server_thread()

        @classmethod
        def _start_server_thread(cls):
            connections_override = cls._make_connections_override()
            for conn in connections_override.values():
                # Explicitly enable thread-shareability for this connection.
                conn.inc_thread_sharing()

            cls.server_thread = cls._create_server_thread(connections_override)
            cls.server_thread.daemon = True
            cls.server_thread.start()
            cls.addClassCleanup(cls._terminate_thread)

            # Wait for the live server to be ready
            cls.server_thread.is_ready.wait()
            if cls.server_thread.error:
                raise cls.server_thread.error

        @classmethod
        def _create_server_thread(cls, connections_override):
            return cls.server_thread_class(
                cls.host,
                cls.static_handler,
                connections_override=connections_override,
                port=cls.port,
            )

        @classmethod
        def _terminate_thread(cls):
            # Terminate the live server's thread.
            cls.server_thread.terminate()
            # Restore shared connections' non-shareability.
            for conn in cls.server_thread.connections_override.values():
                conn.dec_thread_sharing()

    class SerializeMixin:
        """
        Enforce serialization of TestCases that share a common resource.

        Define a common 'lockfile' for each set of TestCases to serialize. This
        file must exist on the filesystem.

        Place it early in the MRO in order to isolate setUpClass()/tearDownClass().
        """

        lockfile = None

        def __init_subclass__(cls, /, **kwargs):
            super().__init_subclass__(**kwargs)
            if cls.lockfile is None:
                raise ValueError(
                    "{}.lockfile isn't set. Set it to a unique value "
                    "in the base class.".format(cls.__name__)
                )

        @classmethod
        def setUpClass(cls):
            cls._lockfile = open(cls.lockfile)
            cls.addClassCleanup(cls._lockfile.close)
            locks.lock(cls._lockfile, locks.LOCK_EX)
            super().setUpClass()