first comit

venv/lib/python3.10/site-packages/django/test/__init__.py

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+"""Django Unit Test framework."""
+
+from django.test.client import AsyncClient, AsyncRequestFactory, Client, RequestFactory
+from django.test.testcases import (
+    LiveServerTestCase,
+    SimpleTestCase,
+    TestCase,
+    TransactionTestCase,
+    skipIfDBFeature,
+    skipUnlessAnyDBFeature,
+    skipUnlessDBFeature,
+)
+from django.test.utils import (
+    ignore_warnings,
+    modify_settings,
+    override_settings,
+    override_system_checks,
+    tag,
+)
+
+__all__ = [
+    "AsyncClient",
+    "AsyncRequestFactory",
+    "Client",
+    "RequestFactory",
+    "TestCase",
+    "TransactionTestCase",
+    "SimpleTestCase",
+    "LiveServerTestCase",
+    "skipIfDBFeature",
+    "skipUnlessAnyDBFeature",
+    "skipUnlessDBFeature",
+    "ignore_warnings",
+    "modify_settings",
+    "override_settings",
+    "override_system_checks",
+    "tag",
+]

venv/lib/python3.10/site-packages/django/test/html.py

@@ -0,0 +1,273 @@
+"""Compare two HTML documents."""
+
+import html
+from html.parser import HTMLParser
+
+from django.utils.html import VOID_ELEMENTS
+from django.utils.regex_helper import _lazy_re_compile
+
+# ASCII whitespace is U+0009 TAB, U+000A LF, U+000C FF, U+000D CR, or U+0020
+# SPACE.
+# https://infra.spec.whatwg.org/#ascii-whitespace
+ASCII_WHITESPACE = _lazy_re_compile(r"[\t\n\f\r ]+")
+
+# https://html.spec.whatwg.org/#attributes-3
+BOOLEAN_ATTRIBUTES = {
+    "allowfullscreen",
+    "async",
+    "autofocus",
+    "autoplay",
+    "checked",
+    "controls",
+    "default",
+    "defer ",
+    "disabled",
+    "formnovalidate",
+    "hidden",
+    "ismap",
+    "itemscope",
+    "loop",
+    "multiple",
+    "muted",
+    "nomodule",
+    "novalidate",
+    "open",
+    "playsinline",
+    "readonly",
+    "required",
+    "reversed",
+    "selected",
+    # Attributes for deprecated tags.
+    "truespeed",
+}
+
+
+def normalize_whitespace(string):
+    return ASCII_WHITESPACE.sub(" ", string)
+
+
+def normalize_attributes(attributes):
+    normalized = []
+    for name, value in attributes:
+        if name == "class" and value:
+            # Special case handling of 'class' attribute, so that comparisons
+            # of DOM instances are not sensitive to ordering of classes.
+            value = " ".join(
+                sorted(value for value in ASCII_WHITESPACE.split(value) if value)
+            )
+        # Boolean attributes without a value is same as attribute with value
+        # that equals the attributes name. For example:
+        #   <input checked> == <input checked="checked">
+        if name in BOOLEAN_ATTRIBUTES:
+            if not value or value == name:
+                value = None
+        elif value is None:
+            value = ""
+        normalized.append((name, value))
+    return normalized
+
+
+class Element:
+    def __init__(self, name, attributes):
+        self.name = name
+        self.attributes = sorted(attributes)
+        self.children = []
+
+    def append(self, element):
+        if isinstance(element, str):
+            element = normalize_whitespace(element)
+            if self.children and isinstance(self.children[-1], str):
+                self.children[-1] += element
+                self.children[-1] = normalize_whitespace(self.children[-1])
+                return
+        elif self.children:
+            # removing last children if it is only whitespace
+            # this can result in incorrect dom representations since
+            # whitespace between inline tags like <span> is significant
+            if isinstance(self.children[-1], str) and self.children[-1].isspace():
+                self.children.pop()
+        if element:
+            self.children.append(element)
+
+    def finalize(self):
+        def rstrip_last_element(children):
+            if children and isinstance(children[-1], str):
+                children[-1] = children[-1].rstrip()
+                if not children[-1]:
+                    children.pop()
+                    children = rstrip_last_element(children)
+            return children
+
+        rstrip_last_element(self.children)
+        for i, child in enumerate(self.children):
+            if isinstance(child, str):
+                self.children[i] = child.strip()
+            elif hasattr(child, "finalize"):
+                child.finalize()
+
+    def __eq__(self, element):
+        if not hasattr(element, "name") or self.name != element.name:
+            return False
+        if self.attributes != element.attributes:
+            return False
+        return self.children == element.children
+
+    def __hash__(self):
+        return hash((self.name, *self.attributes))
+
+    def _count(self, element, count=True):
+        if not isinstance(element, str) and self == element:
+            return 1
+        if isinstance(element, RootElement) and self.children == element.children:
+            return 1
+        i = 0
+        elem_child_idx = 0
+        for child in self.children:
+            # child is text content and element is also text content, then
+            # make a simple "text" in "text"
+            if isinstance(child, str):
+                if isinstance(element, str):
+                    if count:
+                        i += child.count(element)
+                    elif element in child:
+                        return 1
+            else:
+                # Look for element wholly within this child.
+                i += child._count(element, count=count)
+                if not count and i:
+                    return i
+                # Also look for a sequence of element's children among self's
+                # children. self.children == element.children is tested above,
+                # but will fail if self has additional children. Ex: '<a/><b/>'
+                # is contained in '<a/><b/><c/>'.
+                if isinstance(element, RootElement) and element.children:
+                    elem_child = element.children[elem_child_idx]
+                    # Start or continue match, advance index.
+                    if elem_child == child:
+                        elem_child_idx += 1
+                        # Match found, reset index.
+                        if elem_child_idx == len(element.children):
+                            i += 1
+                            elem_child_idx = 0
+                    # No match, reset index.
+                    else:
+                        elem_child_idx = 0
+        return i
+
+    def __contains__(self, element):
+        return self._count(element, count=False) > 0
+
+    def count(self, element):
+        return self._count(element, count=True)
+
+    def __getitem__(self, key):
+        return self.children[key]
+
+    def __str__(self):
+        output = "<%s" % self.name
+        for key, value in self.attributes:
+            if value is not None:
+                output += ' %s="%s"' % (key, value)
+            else:
+                output += " %s" % key
+        if self.children:
+            output += ">\n"
+            output += "".join(
+                [
+                    html.escape(c) if isinstance(c, str) else str(c)
+                    for c in self.children
+                ]
+            )
+            output += "\n</%s>" % self.name
+        else:
+            output += ">"
+        return output
+
+    def __repr__(self):
+        return str(self)
+
+
+class RootElement(Element):
+    def __init__(self):
+        super().__init__(None, ())
+
+    def __str__(self):
+        return "".join(
+            [html.escape(c) if isinstance(c, str) else str(c) for c in self.children]
+        )
+
+
+class HTMLParseError(Exception):
+    pass
+
+
+class Parser(HTMLParser):
+    def __init__(self):
+        super().__init__()
+        self.root = RootElement()
+        self.open_tags = []
+        self.element_positions = {}
+
+    def error(self, msg):
+        raise HTMLParseError(msg, self.getpos())
+
+    def format_position(self, position=None, element=None):
+        if not position and element:
+            position = self.element_positions[element]
+        if position is None:
+            position = self.getpos()
+        if hasattr(position, "lineno"):
+            position = position.lineno, position.offset
+        return "Line %d, Column %d" % position
+
+    @property
+    def current(self):
+        if self.open_tags:
+            return self.open_tags[-1]
+        else:
+            return self.root
+
+    def handle_startendtag(self, tag, attrs):
+        self.handle_starttag(tag, attrs)
+        if tag not in VOID_ELEMENTS:
+            self.handle_endtag(tag)
+
+    def handle_starttag(self, tag, attrs):
+        attrs = normalize_attributes(attrs)
+        element = Element(tag, attrs)
+        self.current.append(element)
+        if tag not in VOID_ELEMENTS:
+            self.open_tags.append(element)
+        self.element_positions[element] = self.getpos()
+
+    def handle_endtag(self, tag):
+        if not self.open_tags:
+            self.error("Unexpected end tag `%s` (%s)" % (tag, self.format_position()))
+        element = self.open_tags.pop()
+        while element.name != tag:
+            if not self.open_tags:
+                self.error(
+                    "Unexpected end tag `%s` (%s)" % (tag, self.format_position())
+                )
+            element = self.open_tags.pop()
+
+    def handle_data(self, data):
+        self.current.append(data)
+
+
+def parse_html(html):
+    """
+    Take a string that contains HTML and turn it into a Python object structure
+    that can be easily compared against other HTML on semantic equivalence.
+    Syntactical differences like which quotation is used on arguments will be
+    ignored.
+    """
+    parser = Parser()
+    parser.feed(html)
+    parser.close()
+    document = parser.root
+    document.finalize()
+    # Removing ROOT element if it's not necessary
+    if len(document.children) == 1 and not isinstance(document.children[0], str):
+        document = document.children[0]
+    return document

venv/lib/python3.10/site-packages/django/test/selenium.py

@@ -0,0 +1,136 @@
+import sys
+import unittest
+from contextlib import contextmanager
+
+from django.test import LiveServerTestCase, tag
+from django.utils.functional import classproperty
+from django.utils.module_loading import import_string
+from django.utils.text import capfirst
+
+
+class SeleniumTestCaseBase(type(LiveServerTestCase)):
+    # List of browsers to dynamically create test classes for.
+    browsers = []
+    # A selenium hub URL to test against.
+    selenium_hub = None
+    # The external host Selenium Hub can reach.
+    external_host = None
+    # Sentinel value to differentiate browser-specific instances.
+    browser = None
+    # Run browsers in headless mode.
+    headless = False
+
+    def __new__(cls, name, bases, attrs):
+        """
+        Dynamically create new classes and add them to the test module when
+        multiple browsers specs are provided (e.g. --selenium=firefox,chrome).
+        """
+        test_class = super().__new__(cls, name, bases, attrs)
+        # If the test class is either browser-specific or a test base, return it.
+        if test_class.browser or not any(
+            name.startswith("test") and callable(value) for name, value in attrs.items()
+        ):
+            return test_class
+        elif test_class.browsers:
+            # Reuse the created test class to make it browser-specific.
+            # We can't rename it to include the browser name or create a
+            # subclass like we do with the remaining browsers as it would
+            # either duplicate tests or prevent pickling of its instances.
+            first_browser = test_class.browsers[0]
+            test_class.browser = first_browser
+            # Listen on an external interface if using a selenium hub.
+            host = test_class.host if not test_class.selenium_hub else "0.0.0.0"
+            test_class.host = host
+            test_class.external_host = cls.external_host
+            # Create subclasses for each of the remaining browsers and expose
+            # them through the test's module namespace.
+            module = sys.modules[test_class.__module__]
+            for browser in test_class.browsers[1:]:
+                browser_test_class = cls.__new__(
+                    cls,
+                    "%s%s" % (capfirst(browser), name),
+                    (test_class,),
+                    {
+                        "browser": browser,
+                        "host": host,
+                        "external_host": cls.external_host,
+                        "__module__": test_class.__module__,
+                    },
+                )
+                setattr(module, browser_test_class.__name__, browser_test_class)
+            return test_class
+        # If no browsers were specified, skip this class (it'll still be discovered).
+        return unittest.skip("No browsers specified.")(test_class)
+
+    @classmethod
+    def import_webdriver(cls, browser):
+        return import_string("selenium.webdriver.%s.webdriver.WebDriver" % browser)
+
+    @classmethod
+    def import_options(cls, browser):
+        return import_string("selenium.webdriver.%s.options.Options" % browser)
+
+    @classmethod
+    def get_capability(cls, browser):
+        from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
+
+        return getattr(DesiredCapabilities, browser.upper())
+
+    def create_options(self):
+        options = self.import_options(self.browser)()
+        if self.headless:
+            match self.browser:
+                case "chrome":
+                    options.add_argument("--headless=new")
+                case "firefox":
+                    options.add_argument("-headless")
+        return options
+
+    def create_webdriver(self):
+        options = self.create_options()
+        if self.selenium_hub:
+            from selenium import webdriver
+
+            for key, value in self.get_capability(self.browser).items():
+                options.set_capability(key, value)
+
+            return webdriver.Remote(command_executor=self.selenium_hub, options=options)
+        return self.import_webdriver(self.browser)(options=options)
+
+
+@tag("selenium")
+class SeleniumTestCase(LiveServerTestCase, metaclass=SeleniumTestCaseBase):
+    implicit_wait = 10
+    external_host = None
+
+    @classproperty
+    def live_server_url(cls):
+        return "http://%s:%s" % (cls.external_host or cls.host, cls.server_thread.port)
+
+    @classproperty
+    def allowed_host(cls):
+        return cls.external_host or cls.host
+
+    @classmethod
+    def setUpClass(cls):
+        cls.selenium = cls.create_webdriver()
+        cls.selenium.implicitly_wait(cls.implicit_wait)
+        super().setUpClass()
+        cls.addClassCleanup(cls._quit_selenium)
+
+    @classmethod
+    def _quit_selenium(cls):
+        # quit() the WebDriver before attempting to terminate and join the
+        # single-threaded LiveServerThread to avoid a dead lock if the browser
+        # kept a connection alive.
+        if hasattr(cls, "selenium"):
+            cls.selenium.quit()
+
+    @contextmanager
+    def disable_implicit_wait(self):
+        """Disable the default implicit wait."""
+        self.selenium.implicitly_wait(0)
+        try:
+            yield
+        finally:
+            self.selenium.implicitly_wait(self.implicit_wait)

venv/lib/python3.10/site-packages/django/test/signals.py

@@ -0,0 +1,273 @@
+import os
+import time
+import warnings
+
+from asgiref.local import Local
+
+from django.apps import apps
+from django.core.exceptions import ImproperlyConfigured
+from django.core.signals import setting_changed
+from django.db import connections, router
+from django.db.utils import ConnectionRouter
+from django.dispatch import Signal, receiver
+from django.utils import timezone
+from django.utils.formats import FORMAT_SETTINGS, reset_format_cache
+from django.utils.functional import empty
+from django.utils.module_loading import import_string
+
+template_rendered = Signal()
+
+# Most setting_changed receivers are supposed to be added below,
+# except for cases where the receiver is related to a contrib app.
+
+# Settings that may not work well when using 'override_settings' (#19031)
+COMPLEX_OVERRIDE_SETTINGS = {"DATABASES"}
+
+
+@receiver(setting_changed)
+def clear_cache_handlers(*, setting, **kwargs):
+    if setting == "CACHES":
+        from django.core.cache import caches, close_caches
+
+        close_caches()
+        caches._settings = caches.settings = caches.configure_settings(None)
+        caches._connections = Local()
+
+
+@receiver(setting_changed)
+def update_installed_apps(*, setting, **kwargs):
+    if setting == "INSTALLED_APPS":
+        # Rebuild any AppDirectoriesFinder instance.
+        from django.contrib.staticfiles.finders import get_finder
+
+        get_finder.cache_clear()
+        # Rebuild management commands cache
+        from django.core.management import get_commands
+
+        get_commands.cache_clear()
+        # Rebuild get_app_template_dirs cache.
+        from django.template.utils import get_app_template_dirs
+
+        get_app_template_dirs.cache_clear()
+        # Rebuild translations cache.
+        from django.utils.translation import trans_real
+
+        trans_real._translations = {}
+
+
+@receiver(setting_changed)
+def update_connections_time_zone(*, setting, **kwargs):
+    if setting == "TIME_ZONE":
+        # Reset process time zone
+        if hasattr(time, "tzset"):
+            if kwargs["value"]:
+                os.environ["TZ"] = kwargs["value"]
+            else:
+                os.environ.pop("TZ", None)
+            time.tzset()
+
+        # Reset local time zone cache
+        timezone.get_default_timezone.cache_clear()
+
+    # Reset the database connections' time zone
+    if setting in {"TIME_ZONE", "USE_TZ"}:
+        for conn in connections.all(initialized_only=True):
+            try:
+                del conn.timezone
+            except AttributeError:
+                pass
+            try:
+                del conn.timezone_name
+            except AttributeError:
+                pass
+            conn.ensure_timezone()
+
+
+@receiver(setting_changed)
+def clear_routers_cache(*, setting, **kwargs):
+    if setting == "DATABASE_ROUTERS":
+        router.routers = ConnectionRouter().routers
+
+
+@receiver(setting_changed)
+def reset_template_engines(*, setting, **kwargs):
+    if setting in {
+        "TEMPLATES",
+        "DEBUG",
+        "INSTALLED_APPS",
+    }:
+        from django.template import engines
+
+        try:
+            del engines.templates
+        except AttributeError:
+            pass
+        engines._templates = None
+        engines._engines = {}
+        from django.template.engine import Engine
+
+        Engine.get_default.cache_clear()
+        from django.forms.renderers import get_default_renderer
+
+        get_default_renderer.cache_clear()
+
+
+@receiver(setting_changed)
+def storages_changed(*, setting, **kwargs):
+    from django.contrib.staticfiles.storage import staticfiles_storage
+    from django.core.files.storage import default_storage, storages
+
+    if setting in (
+        "STORAGES",
+        "STATIC_ROOT",
+        "STATIC_URL",
+    ):
+        try:
+            del storages.backends
+        except AttributeError:
+            pass
+        storages._backends = None
+        storages._storages = {}
+
+        default_storage._wrapped = empty
+        staticfiles_storage._wrapped = empty
+
+
+@receiver(setting_changed)
+def clear_serializers_cache(*, setting, **kwargs):
+    if setting == "SERIALIZATION_MODULES":
+        from django.core import serializers
+
+        serializers._serializers = {}
+
+
+@receiver(setting_changed)
+def language_changed(*, setting, **kwargs):
+    if setting in {"LANGUAGES", "LANGUAGE_CODE", "LOCALE_PATHS"}:
+        from django.utils.translation import trans_real
+
+        trans_real._default = None
+        trans_real._active = Local()
+    if setting in {"LANGUAGES", "LOCALE_PATHS"}:
+        from django.utils.translation import trans_real
+
+        trans_real._translations = {}
+        trans_real.check_for_language.cache_clear()
+
+
+@receiver(setting_changed)
+def localize_settings_changed(*, setting, **kwargs):
+    if setting in FORMAT_SETTINGS or setting == "USE_THOUSAND_SEPARATOR":
+        reset_format_cache()
+
+
+# RemovedInDjango51Warning.
+@receiver(setting_changed)
+def file_storage_changed(*, setting, **kwargs):
+    if setting == "DEFAULT_FILE_STORAGE":
+        from django.conf import DEFAULT_STORAGE_ALIAS
+        from django.core.files.storage import default_storage, storages
+
+        try:
+            del storages.backends
+        except AttributeError:
+            pass
+        storages._storages[DEFAULT_STORAGE_ALIAS] = import_string(kwargs["value"])()
+        default_storage._wrapped = empty
+
+
+@receiver(setting_changed)
+def complex_setting_changed(*, enter, setting, **kwargs):
+    if enter and setting in COMPLEX_OVERRIDE_SETTINGS:
+        # Considering the current implementation of the signals framework,
+        # this stacklevel shows the line containing the override_settings call.
+        warnings.warn(
+            f"Overriding setting {setting} can lead to unexpected behavior.",
+            stacklevel=5,
+        )
+
+
+@receiver(setting_changed)
+def root_urlconf_changed(*, setting, **kwargs):
+    if setting == "ROOT_URLCONF":
+        from django.urls import clear_url_caches, set_urlconf
+
+        clear_url_caches()
+        set_urlconf(None)
+
+
+@receiver(setting_changed)
+def static_storage_changed(*, setting, **kwargs):
+    if setting in {
+        "STATICFILES_STORAGE",
+        "STATIC_ROOT",
+        "STATIC_URL",
+    }:
+        from django.contrib.staticfiles.storage import staticfiles_storage
+
+        staticfiles_storage._wrapped = empty
+
+    # RemovedInDjango51Warning.
+    if setting == "STATICFILES_STORAGE":
+        from django.conf import STATICFILES_STORAGE_ALIAS
+        from django.core.files.storage import storages
+
+        try:
+            del storages.backends
+        except AttributeError:
+            pass
+        storages._storages[STATICFILES_STORAGE_ALIAS] = import_string(kwargs["value"])()
+
+
+@receiver(setting_changed)
+def static_finders_changed(*, setting, **kwargs):
+    if setting in {
+        "STATICFILES_DIRS",
+        "STATIC_ROOT",
+    }:
+        from django.contrib.staticfiles.finders import get_finder
+
+        get_finder.cache_clear()
+
+
+@receiver(setting_changed)
+def auth_password_validators_changed(*, setting, **kwargs):
+    if setting == "AUTH_PASSWORD_VALIDATORS":
+        from django.contrib.auth.password_validation import (
+            get_default_password_validators,
+        )
+
+        get_default_password_validators.cache_clear()
+
+
+@receiver(setting_changed)
+def user_model_swapped(*, setting, **kwargs):
+    if setting == "AUTH_USER_MODEL":
+        apps.clear_cache()
+        try:
+            from django.contrib.auth import get_user_model
+
+            UserModel = get_user_model()
+        except ImproperlyConfigured:
+            # Some tests set an invalid AUTH_USER_MODEL.
+            pass
+        else:
+            from django.contrib.auth import backends
+
+            backends.UserModel = UserModel
+
+            from django.contrib.auth import forms
+
+            forms.UserModel = UserModel
+
+            from django.contrib.auth.handlers import modwsgi
+
+            modwsgi.UserModel = UserModel
+
+            from django.contrib.auth.management.commands import changepassword
+
+            changepassword.UserModel = UserModel
+
+            from django.contrib.auth import views
+
+            views.UserModel = UserModel

venv/lib/python3.10/site-packages/django/test/utils.py

@@ -0,0 +1,984 @@
+import collections
+import logging
+import os
+import re
+import sys
+import time
+import warnings
+from contextlib import contextmanager
+from functools import wraps
+from io import StringIO
+from itertools import chain
+from types import SimpleNamespace
+from unittest import TestCase, skipIf, skipUnless
+from xml.dom.minidom import Node, parseString
+
+from asgiref.sync import iscoroutinefunction
+
+from django.apps import apps
+from django.apps.registry import Apps
+from django.conf import UserSettingsHolder, settings
+from django.core import mail
+from django.core.exceptions import ImproperlyConfigured
+from django.core.signals import request_started, setting_changed
+from django.db import DEFAULT_DB_ALIAS, connections, reset_queries
+from django.db.models.options import Options
+from django.template import Template
+from django.test.signals import template_rendered
+from django.urls import get_script_prefix, set_script_prefix
+from django.utils.translation import deactivate
+
+try:
+    import jinja2
+except ImportError:
+    jinja2 = None
+
+
+__all__ = (
+    "Approximate",
+    "ContextList",
+    "isolate_lru_cache",
+    "get_runner",
+    "CaptureQueriesContext",
+    "ignore_warnings",
+    "isolate_apps",
+    "modify_settings",
+    "override_settings",
+    "override_system_checks",
+    "tag",
+    "requires_tz_support",
+    "setup_databases",
+    "setup_test_environment",
+    "teardown_test_environment",
+)
+
+TZ_SUPPORT = hasattr(time, "tzset")
+
+
+class Approximate:
+    def __init__(self, val, places=7):
+        self.val = val
+        self.places = places
+
+    def __repr__(self):
+        return repr(self.val)
+
+    def __eq__(self, other):
+        return self.val == other or round(abs(self.val - other), self.places) == 0
+
+
+class ContextList(list):
+    """
+    A wrapper that provides direct key access to context items contained
+    in a list of context objects.
+    """
+
+    def __getitem__(self, key):
+        if isinstance(key, str):
+            for subcontext in self:
+                if key in subcontext:
+                    return subcontext[key]
+            raise KeyError(key)
+        else:
+            return super().__getitem__(key)
+
+    def get(self, key, default=None):
+        try:
+            return self.__getitem__(key)
+        except KeyError:
+            return default
+
+    def __contains__(self, key):
+        try:
+            self[key]
+        except KeyError:
+            return False
+        return True
+
+    def keys(self):
+        """
+        Flattened keys of subcontexts.
+        """
+        return set(chain.from_iterable(d for subcontext in self for d in subcontext))
+
+
+def instrumented_test_render(self, context):
+    """
+    An instrumented Template render method, providing a signal that can be
+    intercepted by the test Client.
+    """
+    template_rendered.send(sender=self, template=self, context=context)
+    return self.nodelist.render(context)
+
+
+class _TestState:
+    pass
+
+
+def setup_test_environment(debug=None):
+    """
+    Perform global pre-test setup, such as installing the instrumented template
+    renderer and setting the email backend to the locmem email backend.
+    """
+    if hasattr(_TestState, "saved_data"):
+        # Executing this function twice would overwrite the saved values.
+        raise RuntimeError(
+            "setup_test_environment() was already called and can't be called "
+            "again without first calling teardown_test_environment()."
+        )
+
+    if debug is None:
+        debug = settings.DEBUG
+
+    saved_data = SimpleNamespace()
+    _TestState.saved_data = saved_data
+
+    saved_data.allowed_hosts = settings.ALLOWED_HOSTS
+    # Add the default host of the test client.
+    settings.ALLOWED_HOSTS = [*settings.ALLOWED_HOSTS, "testserver"]
+
+    saved_data.debug = settings.DEBUG
+    settings.DEBUG = debug
+
+    saved_data.email_backend = settings.EMAIL_BACKEND
+    settings.EMAIL_BACKEND = "django.core.mail.backends.locmem.EmailBackend"
+
+    saved_data.template_render = Template._render
+    Template._render = instrumented_test_render
+
+    mail.outbox = []
+
+    deactivate()
+
+
+def teardown_test_environment():
+    """
+    Perform any global post-test teardown, such as restoring the original
+    template renderer and restoring the email sending functions.
+    """
+    saved_data = _TestState.saved_data
+
+    settings.ALLOWED_HOSTS = saved_data.allowed_hosts
+    settings.DEBUG = saved_data.debug
+    settings.EMAIL_BACKEND = saved_data.email_backend
+    Template._render = saved_data.template_render
+
+    del _TestState.saved_data
+    del mail.outbox
+
+
+def setup_databases(
+    verbosity,
+    interactive,
+    *,
+    time_keeper=None,
+    keepdb=False,
+    debug_sql=False,
+    parallel=0,
+    aliases=None,
+    serialized_aliases=None,
+    **kwargs,
+):
+    """Create the test databases."""
+    if time_keeper is None:
+        time_keeper = NullTimeKeeper()
+
+    test_databases, mirrored_aliases = get_unique_databases_and_mirrors(aliases)
+
+    old_names = []
+
+    for db_name, aliases in test_databases.values():
+        first_alias = None
+        for alias in aliases:
+            connection = connections[alias]
+            old_names.append((connection, db_name, first_alias is None))
+
+            # Actually create the database for the first connection
+            if first_alias is None:
+                first_alias = alias
+                with time_keeper.timed("  Creating '%s'" % alias):
+                    serialize_alias = (
+                        serialized_aliases is None or alias in serialized_aliases
+                    )
+                    connection.creation.create_test_db(
+                        verbosity=verbosity,
+                        autoclobber=not interactive,
+                        keepdb=keepdb,
+                        serialize=serialize_alias,
+                    )
+                if parallel > 1:
+                    for index in range(parallel):
+                        with time_keeper.timed("  Cloning '%s'" % alias):
+                            connection.creation.clone_test_db(
+                                suffix=str(index + 1),
+                                verbosity=verbosity,
+                                keepdb=keepdb,
+                            )
+            # Configure all other connections as mirrors of the first one
+            else:
+                connections[alias].creation.set_as_test_mirror(
+                    connections[first_alias].settings_dict
+                )
+
+    # Configure the test mirrors.
+    for alias, mirror_alias in mirrored_aliases.items():
+        connections[alias].creation.set_as_test_mirror(
+            connections[mirror_alias].settings_dict
+        )
+
+    if debug_sql:
+        for alias in connections:
+            connections[alias].force_debug_cursor = True
+
+    return old_names
+
+
+def iter_test_cases(tests):
+    """
+    Return an iterator over a test suite's unittest.TestCase objects.
+
+    The tests argument can also be an iterable of TestCase objects.
+    """
+    for test in tests:
+        if isinstance(test, str):
+            # Prevent an unfriendly RecursionError that can happen with
+            # strings.
+            raise TypeError(
+                f"Test {test!r} must be a test case or test suite not string "
+                f"(was found in {tests!r})."
+            )
+        if isinstance(test, TestCase):
+            yield test
+        else:
+            # Otherwise, assume it is a test suite.
+            yield from iter_test_cases(test)
+
+
+def dependency_ordered(test_databases, dependencies):
+    """
+    Reorder test_databases into an order that honors the dependencies
+    described in TEST[DEPENDENCIES].
+    """
+    ordered_test_databases = []
+    resolved_databases = set()
+
+    # Maps db signature to dependencies of all its aliases
+    dependencies_map = {}
+
+    # Check that no database depends on its own alias
+    for sig, (_, aliases) in test_databases:
+        all_deps = set()
+        for alias in aliases:
+            all_deps.update(dependencies.get(alias, []))
+        if not all_deps.isdisjoint(aliases):
+            raise ImproperlyConfigured(
+                "Circular dependency: databases %r depend on each other, "
+                "but are aliases." % aliases
+            )
+        dependencies_map[sig] = all_deps
+
+    while test_databases:
+        changed = False
+        deferred = []
+
+        # Try to find a DB that has all its dependencies met
+        for signature, (db_name, aliases) in test_databases:
+            if dependencies_map[signature].issubset(resolved_databases):
+                resolved_databases.update(aliases)
+                ordered_test_databases.append((signature, (db_name, aliases)))
+                changed = True
+            else:
+                deferred.append((signature, (db_name, aliases)))
+
+        if not changed:
+            raise ImproperlyConfigured("Circular dependency in TEST[DEPENDENCIES]")
+        test_databases = deferred
+    return ordered_test_databases
+
+
+def get_unique_databases_and_mirrors(aliases=None):
+    """
+    Figure out which databases actually need to be created.
+
+    Deduplicate entries in DATABASES that correspond the same database or are
+    configured as test mirrors.
+
+    Return two values:
+    - test_databases: ordered mapping of signatures to (name, list of aliases)
+                      where all aliases share the same underlying database.
+    - mirrored_aliases: mapping of mirror aliases to original aliases.
+    """
+    if aliases is None:
+        aliases = connections
+    mirrored_aliases = {}
+    test_databases = {}
+    dependencies = {}
+    default_sig = connections[DEFAULT_DB_ALIAS].creation.test_db_signature()
+
+    for alias in connections:
+        connection = connections[alias]
+        test_settings = connection.settings_dict["TEST"]
+
+        if test_settings["MIRROR"]:
+            # If the database is marked as a test mirror, save the alias.
+            mirrored_aliases[alias] = test_settings["MIRROR"]
+        elif alias in aliases:
+            # Store a tuple with DB parameters that uniquely identify it.
+            # If we have two aliases with the same values for that tuple,
+            # we only need to create the test database once.
+            item = test_databases.setdefault(
+                connection.creation.test_db_signature(),
+                (connection.settings_dict["NAME"], []),
+            )
+            # The default database must be the first because data migrations
+            # use the default alias by default.
+            if alias == DEFAULT_DB_ALIAS:
+                item[1].insert(0, alias)
+            else:
+                item[1].append(alias)
+
+            if "DEPENDENCIES" in test_settings:
+                dependencies[alias] = test_settings["DEPENDENCIES"]
+            else:
+                if (
+                    alias != DEFAULT_DB_ALIAS
+                    and connection.creation.test_db_signature() != default_sig
+                ):
+                    dependencies[alias] = test_settings.get(
+                        "DEPENDENCIES", [DEFAULT_DB_ALIAS]
+                    )
+
+    test_databases = dict(dependency_ordered(test_databases.items(), dependencies))
+    return test_databases, mirrored_aliases
+
+
+def teardown_databases(old_config, verbosity, parallel=0, keepdb=False):
+    """Destroy all the non-mirror databases."""
+    for connection, old_name, destroy in old_config:
+        if destroy:
+            if parallel > 1:
+                for index in range(parallel):
+                    connection.creation.destroy_test_db(
+                        suffix=str(index + 1),
+                        verbosity=verbosity,
+                        keepdb=keepdb,
+                    )
+            connection.creation.destroy_test_db(old_name, verbosity, keepdb)
+
+
+def get_runner(settings, test_runner_class=None):
+    test_runner_class = test_runner_class or settings.TEST_RUNNER
+    test_path = test_runner_class.split(".")
+    # Allow for relative paths
+    if len(test_path) > 1:
+        test_module_name = ".".join(test_path[:-1])
+    else:
+        test_module_name = "."
+    test_module = __import__(test_module_name, {}, {}, test_path[-1])
+    return getattr(test_module, test_path[-1])
+
+
+class TestContextDecorator:
+    """
+    A base class that can either be used as a context manager during tests
+    or as a test function or unittest.TestCase subclass decorator to perform
+    temporary alterations.
+
+    `attr_name`: attribute assigned the return value of enable() if used as
+                 a class decorator.
+
+    `kwarg_name`: keyword argument passing the return value of enable() if
+                  used as a function decorator.
+    """
+
+    def __init__(self, attr_name=None, kwarg_name=None):
+        self.attr_name = attr_name
+        self.kwarg_name = kwarg_name
+
+    def enable(self):
+        raise NotImplementedError
+
+    def disable(self):
+        raise NotImplementedError
+
+    def __enter__(self):
+        return self.enable()
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.disable()
+
+    def decorate_class(self, cls):
+        if issubclass(cls, TestCase):
+            decorated_setUp = cls.setUp
+
+            def setUp(inner_self):
+                context = self.enable()
+                inner_self.addCleanup(self.disable)
+                if self.attr_name:
+                    setattr(inner_self, self.attr_name, context)
+                decorated_setUp(inner_self)
+
+            cls.setUp = setUp
+            return cls
+        raise TypeError("Can only decorate subclasses of unittest.TestCase")
+
+    def decorate_callable(self, func):
+        if iscoroutinefunction(func):
+            # If the inner function is an async function, we must execute async
+            # as well so that the `with` statement executes at the right time.
+            @wraps(func)
+            async def inner(*args, **kwargs):
+                with self as context:
+                    if self.kwarg_name:
+                        kwargs[self.kwarg_name] = context
+                    return await func(*args, **kwargs)
+
+        else:
+
+            @wraps(func)
+            def inner(*args, **kwargs):
+                with self as context:
+                    if self.kwarg_name:
+                        kwargs[self.kwarg_name] = context
+                    return func(*args, **kwargs)
+
+        return inner
+
+    def __call__(self, decorated):
+        if isinstance(decorated, type):
+            return self.decorate_class(decorated)
+        elif callable(decorated):
+            return self.decorate_callable(decorated)
+        raise TypeError("Cannot decorate object of type %s" % type(decorated))
+
+
+class override_settings(TestContextDecorator):
+    """
+    Act as either a decorator or a context manager. If it's a decorator, take a
+    function and return a wrapped function. If it's a contextmanager, use it
+    with the ``with`` statement. In either event, entering/exiting are called
+    before and after, respectively, the function/block is executed.
+    """
+
+    enable_exception = None
+
+    def __init__(self, **kwargs):
+        self.options = kwargs
+        super().__init__()
+
+    def enable(self):
+        # Keep this code at the beginning to leave the settings unchanged
+        # in case it raises an exception because INSTALLED_APPS is invalid.
+        if "INSTALLED_APPS" in self.options:
+            try:
+                apps.set_installed_apps(self.options["INSTALLED_APPS"])
+            except Exception:
+                apps.unset_installed_apps()
+                raise
+        override = UserSettingsHolder(settings._wrapped)
+        for key, new_value in self.options.items():
+            setattr(override, key, new_value)
+        self.wrapped = settings._wrapped
+        settings._wrapped = override
+        for key, new_value in self.options.items():
+            try:
+                setting_changed.send(
+                    sender=settings._wrapped.__class__,
+                    setting=key,
+                    value=new_value,
+                    enter=True,
+                )
+            except Exception as exc:
+                self.enable_exception = exc
+                self.disable()
+
+    def disable(self):
+        if "INSTALLED_APPS" in self.options:
+            apps.unset_installed_apps()
+        settings._wrapped = self.wrapped
+        del self.wrapped
+        responses = []
+        for key in self.options:
+            new_value = getattr(settings, key, None)
+            responses_for_setting = setting_changed.send_robust(
+                sender=settings._wrapped.__class__,
+                setting=key,
+                value=new_value,
+                enter=False,
+            )
+            responses.extend(responses_for_setting)
+        if self.enable_exception is not None:
+            exc = self.enable_exception
+            self.enable_exception = None
+            raise exc
+        for _, response in responses:
+            if isinstance(response, Exception):
+                raise response
+
+    def save_options(self, test_func):
+        if test_func._overridden_settings is None:
+            test_func._overridden_settings = self.options
+        else:
+            # Duplicate dict to prevent subclasses from altering their parent.
+            test_func._overridden_settings = {
+                **test_func._overridden_settings,
+                **self.options,
+            }
+
+    def decorate_class(self, cls):
+        from django.test import SimpleTestCase
+
+        if not issubclass(cls, SimpleTestCase):
+            raise ValueError(
+                "Only subclasses of Django SimpleTestCase can be decorated "
+                "with override_settings"
+            )
+        self.save_options(cls)
+        return cls
+
+
+class modify_settings(override_settings):
+    """
+    Like override_settings, but makes it possible to append, prepend, or remove
+    items instead of redefining the entire list.
+    """
+
+    def __init__(self, *args, **kwargs):
+        if args:
+            # Hack used when instantiating from SimpleTestCase.setUpClass.
+            assert not kwargs
+            self.operations = args[0]
+        else:
+            assert not args
+            self.operations = list(kwargs.items())
+        super(override_settings, self).__init__()
+
+    def save_options(self, test_func):
+        if test_func._modified_settings is None:
+            test_func._modified_settings = self.operations
+        else:
+            # Duplicate list to prevent subclasses from altering their parent.
+            test_func._modified_settings = (
+                list(test_func._modified_settings) + self.operations
+            )
+
+    def enable(self):
+        self.options = {}
+        for name, operations in self.operations:
+            try:
+                # When called from SimpleTestCase.setUpClass, values may be
+                # overridden several times; cumulate changes.
+                value = self.options[name]
+            except KeyError:
+                value = list(getattr(settings, name, []))
+            for action, items in operations.items():
+                # items may be a single value or an iterable.
+                if isinstance(items, str):
+                    items = [items]
+                if action == "append":
+                    value += [item for item in items if item not in value]
+                elif action == "prepend":
+                    value = [item for item in items if item not in value] + value
+                elif action == "remove":
+                    value = [item for item in value if item not in items]
+                else:
+                    raise ValueError("Unsupported action: %s" % action)
+            self.options[name] = value
+        super().enable()
+
+
+class override_system_checks(TestContextDecorator):
+    """
+    Act as a decorator. Override list of registered system checks.
+    Useful when you override `INSTALLED_APPS`, e.g. if you exclude `auth` app,
+    you also need to exclude its system checks.
+    """
+
+    def __init__(self, new_checks, deployment_checks=None):
+        from django.core.checks.registry import registry
+
+        self.registry = registry
+        self.new_checks = new_checks
+        self.deployment_checks = deployment_checks
+        super().__init__()
+
+    def enable(self):
+        self.old_checks = self.registry.registered_checks
+        self.registry.registered_checks = set()
+        for check in self.new_checks:
+            self.registry.register(check, *getattr(check, "tags", ()))
+        self.old_deployment_checks = self.registry.deployment_checks
+        if self.deployment_checks is not None:
+            self.registry.deployment_checks = set()
+            for check in self.deployment_checks:
+                self.registry.register(check, *getattr(check, "tags", ()), deploy=True)
+
+    def disable(self):
+        self.registry.registered_checks = self.old_checks
+        self.registry.deployment_checks = self.old_deployment_checks
+
+
+def compare_xml(want, got):
+    """
+    Try to do a 'xml-comparison' of want and got. Plain string comparison
+    doesn't always work because, for example, attribute ordering should not be
+    important. Ignore comment nodes, processing instructions, document type
+    node, and leading and trailing whitespaces.
+
+    Based on https://github.com/lxml/lxml/blob/master/src/lxml/doctestcompare.py
+    """
+    _norm_whitespace_re = re.compile(r"[ \t\n][ \t\n]+")
+
+    def norm_whitespace(v):
+        return _norm_whitespace_re.sub(" ", v)
+
+    def child_text(element):
+        return "".join(
+            c.data for c in element.childNodes if c.nodeType == Node.TEXT_NODE
+        )
+
+    def children(element):
+        return [c for c in element.childNodes if c.nodeType == Node.ELEMENT_NODE]
+
+    def norm_child_text(element):
+        return norm_whitespace(child_text(element))
+
+    def attrs_dict(element):
+        return dict(element.attributes.items())
+
+    def check_element(want_element, got_element):
+        if want_element.tagName != got_element.tagName:
+            return False
+        if norm_child_text(want_element) != norm_child_text(got_element):
+            return False
+        if attrs_dict(want_element) != attrs_dict(got_element):
+            return False
+        want_children = children(want_element)
+        got_children = children(got_element)
+        if len(want_children) != len(got_children):
+            return False
+        return all(
+            check_element(want, got) for want, got in zip(want_children, got_children)
+        )
+
+    def first_node(document):
+        for node in document.childNodes:
+            if node.nodeType not in (
+                Node.COMMENT_NODE,
+                Node.DOCUMENT_TYPE_NODE,
+                Node.PROCESSING_INSTRUCTION_NODE,
+            ):
+                return node
+
+    want = want.strip().replace("\\n", "\n")
+    got = got.strip().replace("\\n", "\n")
+
+    # If the string is not a complete xml document, we may need to add a
+    # root element. This allow us to compare fragments, like "<foo/><bar/>"
+    if not want.startswith("<?xml"):
+        wrapper = "<root>%s</root>"
+        want = wrapper % want
+        got = wrapper % got
+
+    # Parse the want and got strings, and compare the parsings.
+    want_root = first_node(parseString(want))
+    got_root = first_node(parseString(got))
+
+    return check_element(want_root, got_root)
+
+
+class CaptureQueriesContext:
+    """
+    Context manager that captures queries executed by the specified connection.
+    """
+
+    def __init__(self, connection):
+        self.connection = connection
+
+    def __iter__(self):
+        return iter(self.captured_queries)
+
+    def __getitem__(self, index):
+        return self.captured_queries[index]
+
+    def __len__(self):
+        return len(self.captured_queries)
+
+    @property
+    def captured_queries(self):
+        return self.connection.queries[self.initial_queries : self.final_queries]
+
+    def __enter__(self):
+        self.force_debug_cursor = self.connection.force_debug_cursor
+        self.connection.force_debug_cursor = True
+        # Run any initialization queries if needed so that they won't be
+        # included as part of the count.
+        self.connection.ensure_connection()
+        self.initial_queries = len(self.connection.queries_log)
+        self.final_queries = None
+        request_started.disconnect(reset_queries)
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.connection.force_debug_cursor = self.force_debug_cursor
+        request_started.connect(reset_queries)
+        if exc_type is not None:
+            return
+        self.final_queries = len(self.connection.queries_log)
+
+
+class ignore_warnings(TestContextDecorator):
+    def __init__(self, **kwargs):
+        self.ignore_kwargs = kwargs
+        if "message" in self.ignore_kwargs or "module" in self.ignore_kwargs:
+            self.filter_func = warnings.filterwarnings
+        else:
+            self.filter_func = warnings.simplefilter
+        super().__init__()
+
+    def enable(self):
+        self.catch_warnings = warnings.catch_warnings()
+        self.catch_warnings.__enter__()
+        self.filter_func("ignore", **self.ignore_kwargs)
+
+    def disable(self):
+        self.catch_warnings.__exit__(*sys.exc_info())
+
+
+# On OSes that don't provide tzset (Windows), we can't set the timezone
+# in which the program runs. As a consequence, we must skip tests that
+# don't enforce a specific timezone (with timezone.override or equivalent),
+# or attempt to interpret naive datetimes in the default timezone.
+
+requires_tz_support = skipUnless(
+    TZ_SUPPORT,
+    "This test relies on the ability to run a program in an arbitrary "
+    "time zone, but your operating system isn't able to do that.",
+)
+
+
+@contextmanager
+def extend_sys_path(*paths):
+    """Context manager to temporarily add paths to sys.path."""
+    _orig_sys_path = sys.path[:]
+    sys.path.extend(paths)
+    try:
+        yield
+    finally:
+        sys.path = _orig_sys_path
+
+
+@contextmanager
+def isolate_lru_cache(lru_cache_object):
+    """Clear the cache of an LRU cache object on entering and exiting."""
+    lru_cache_object.cache_clear()
+    try:
+        yield
+    finally:
+        lru_cache_object.cache_clear()
+
+
+@contextmanager
+def captured_output(stream_name):
+    """Return a context manager used by captured_stdout/stdin/stderr
+    that temporarily replaces the sys stream *stream_name* with a StringIO.
+
+    Note: This function and the following ``captured_std*`` are copied
+          from CPython's ``test.support`` module."""
+    orig_stdout = getattr(sys, stream_name)
+    setattr(sys, stream_name, StringIO())
+    try:
+        yield getattr(sys, stream_name)
+    finally:
+        setattr(sys, stream_name, orig_stdout)
+
+
+def captured_stdout():
+    """Capture the output of sys.stdout:
+
+    with captured_stdout() as stdout:
+        print("hello")
+    self.assertEqual(stdout.getvalue(), "hello\n")
+    """
+    return captured_output("stdout")
+
+
+def captured_stderr():
+    """Capture the output of sys.stderr:
+
+    with captured_stderr() as stderr:
+        print("hello", file=sys.stderr)
+    self.assertEqual(stderr.getvalue(), "hello\n")
+    """
+    return captured_output("stderr")
+
+
+def captured_stdin():
+    """Capture the input to sys.stdin:
+
+    with captured_stdin() as stdin:
+        stdin.write('hello\n')
+        stdin.seek(0)
+        # call test code that consumes from sys.stdin
+        captured = input()
+    self.assertEqual(captured, "hello")
+    """
+    return captured_output("stdin")
+
+
+@contextmanager
+def freeze_time(t):
+    """
+    Context manager to temporarily freeze time.time(). This temporarily
+    modifies the time function of the time module. Modules which import the
+    time function directly (e.g. `from time import time`) won't be affected
+    This isn't meant as a public API, but helps reduce some repetitive code in
+    Django's test suite.
+    """
+    _real_time = time.time
+    time.time = lambda: t
+    try:
+        yield
+    finally:
+        time.time = _real_time
+
+
+def require_jinja2(test_func):
+    """
+    Decorator to enable a Jinja2 template engine in addition to the regular
+    Django template engine for a test or skip it if Jinja2 isn't available.
+    """
+    test_func = skipIf(jinja2 is None, "this test requires jinja2")(test_func)
+    return override_settings(
+        TEMPLATES=[
+            {
+                "BACKEND": "django.template.backends.django.DjangoTemplates",
+                "APP_DIRS": True,
+            },
+            {
+                "BACKEND": "django.template.backends.jinja2.Jinja2",
+                "APP_DIRS": True,
+                "OPTIONS": {"keep_trailing_newline": True},
+            },
+        ]
+    )(test_func)
+
+
+class override_script_prefix(TestContextDecorator):
+    """Decorator or context manager to temporary override the script prefix."""
+
+    def __init__(self, prefix):
+        self.prefix = prefix
+        super().__init__()
+
+    def enable(self):
+        self.old_prefix = get_script_prefix()
+        set_script_prefix(self.prefix)
+
+    def disable(self):
+        set_script_prefix(self.old_prefix)
+
+
+class LoggingCaptureMixin:
+    """
+    Capture the output from the 'django' logger and store it on the class's
+    logger_output attribute.
+    """
+
+    def setUp(self):
+        self.logger = logging.getLogger("django")
+        self.old_stream = self.logger.handlers[0].stream
+        self.logger_output = StringIO()
+        self.logger.handlers[0].stream = self.logger_output
+
+    def tearDown(self):
+        self.logger.handlers[0].stream = self.old_stream
+
+
+class isolate_apps(TestContextDecorator):
+    """
+    Act as either a decorator or a context manager to register models defined
+    in its wrapped context to an isolated registry.
+
+    The list of installed apps the isolated registry should contain must be
+    passed as arguments.
+
+    Two optional keyword arguments can be specified:
+
+    `attr_name`: attribute assigned the isolated registry if used as a class
+                 decorator.
+
+    `kwarg_name`: keyword argument passing the isolated registry if used as a
+                  function decorator.
+    """
+
+    def __init__(self, *installed_apps, **kwargs):
+        self.installed_apps = installed_apps
+        super().__init__(**kwargs)
+
+    def enable(self):
+        self.old_apps = Options.default_apps
+        apps = Apps(self.installed_apps)
+        setattr(Options, "default_apps", apps)
+        return apps
+
+    def disable(self):
+        setattr(Options, "default_apps", self.old_apps)
+
+
+class TimeKeeper:
+    def __init__(self):
+        self.records = collections.defaultdict(list)
+
+    @contextmanager
+    def timed(self, name):
+        self.records[name]
+        start_time = time.perf_counter()
+        try:
+            yield
+        finally:
+            end_time = time.perf_counter() - start_time
+            self.records[name].append(end_time)
+
+    def print_results(self):
+        for name, end_times in self.records.items():
+            for record_time in end_times:
+                record = "%s took %.3fs" % (name, record_time)
+                sys.stderr.write(record + os.linesep)
+
+
+class NullTimeKeeper:
+    @contextmanager
+    def timed(self, name):
+        yield
+
+    def print_results(self):
+        pass
+
+
+def tag(*tags):
+    """Decorator to add tags to a test class or method."""
+
+    def decorator(obj):
+        if hasattr(obj, "tags"):
+            obj.tags = obj.tags.union(tags)
+        else:
+            setattr(obj, "tags", set(tags))
+        return obj
+
+    return decorator
+
+
+@contextmanager
+def register_lookup(field, *lookups, lookup_name=None):
+    """
+    Context manager to temporarily register lookups on a model field using
+    lookup_name (or the lookup's lookup_name if not provided).
+    """
+    try:
+        for lookup in lookups:
+            field.register_lookup(lookup, lookup_name)
+        yield
+    finally:
+        for lookup in lookups:
+            field._unregister_lookup(lookup, lookup_name)