text: #!/usr/bin/env python
  import argparse
  import atexit
  import copy
  import gc
  import os
  import shutil
  import socket
  import subprocess
  import sys
  import tempfile
  import warnings
  from pathlib import Path
  
  try:
      import django
  except ImportError as e:
      raise RuntimeError(
          'Django module not found, reference tests/README.rst for instructions.'
      ) from e
  else:
      from django.apps import apps
      from django.conf import settings
      from django.db import connection, connections
      from django.test import TestCase, TransactionTestCase
      from django.test.runner import get_max_test_processes, parallel_type
      from django.test.selenium import SeleniumTestCaseBase
      from django.test.utils import NullTimeKeeper, TimeKeeper, get_runner
      from django.utils.deprecation import RemovedInDjango50Warning
      from django.utils.log import DEFAULT_LOGGING
  
  try:
      import MySQLdb
  except ImportError:
      pass
  else:
      # Ignore informational warnings from QuerySet.explain().
      warnings.filterwarnings('ignore', r'\(1003, *', category=MySQLdb.Warning)
  
  # Make deprecation warnings errors to ensure no usage of deprecated features.
  warnings.simplefilter('error', RemovedInDjango50Warning)
  # Make resource and runtime warning errors to ensure no usage of error prone
  # patterns.
  warnings.simplefilter("error", ResourceWarning)
  warnings.simplefilter("error", RuntimeWarning)
  # Ignore known warnings in test dependencies.
  warnings.filterwarnings("ignore", "'U' mode is deprecated", DeprecationWarning, module='docutils.io')
  
  # Reduce garbage collection frequency to improve performance. Since CPython
  # uses refcounting, garbage collection only collects objects with cyclic
  # references, which are a minority, so the garbage collection threshold can be
  # larger than the default threshold of 700 allocations + deallocations without
  # much increase in memory usage.
  gc.set_threshold(100_000)
  
  RUNTESTS_DIR = os.path.abspath(os.path.dirname(__file__))
  
  TEMPLATE_DIR = os.path.join(RUNTESTS_DIR, 'templates')
  
  # Create a specific subdirectory for the duration of the test suite.
  TMPDIR = tempfile.mkdtemp(prefix='django_')
  # Set the TMPDIR environment variable in addition to tempfile.tempdir
  # so that children processes inherit it.
  tempfile.tempdir = os.environ['TMPDIR'] = TMPDIR
  
  # Removing the temporary TMPDIR.
  atexit.register(shutil.rmtree, TMPDIR)
  
  
  # This is a dict mapping RUNTESTS_DIR subdirectory to subdirectories of that
  # directory to skip when searching for test modules.
  SUBDIRS_TO_SKIP = {
      '': {'import_error_package', 'test_runner_apps'},
      'gis_tests': {'data'},
  }
  
  ALWAYS_INSTALLED_APPS = [
      'django.contrib.contenttypes',
      'django.contrib.auth',
      'django.contrib.sites',
      'django.contrib.sessions',
      'django.contrib.messages',
      'django.contrib.admin.apps.SimpleAdminConfig',
      'django.contrib.staticfiles',
  ]
  
  ALWAYS_MIDDLEWARE = [
      'django.contrib.sessions.middleware.SessionMiddleware',
      'django.middleware.common.CommonMiddleware',
      'django.middleware.csrf.CsrfViewMiddleware',
      'django.contrib.auth.middleware.AuthenticationMiddleware',
      'django.contrib.messages.middleware.MessageMiddleware',
  ]
  
  # Need to add the associated contrib app to INSTALLED_APPS in some cases to
  # avoid "RuntimeError: Model class X doesn't declare an explicit app_label
  # and isn't in an application in INSTALLED_APPS."
  CONTRIB_TESTS_TO_APPS = {
      'deprecation': ['django.contrib.flatpages', 'django.contrib.redirects'],
      'flatpages_tests': ['django.contrib.flatpages'],
      'redirects_tests': ['django.contrib.redirects'],
  }
  
  
  def get_test_modules(gis_enabled):
      """
      Scan the tests directory and yield the names of all test modules.
  
      The yielded names have either one dotted part like "test_runner" or, in
      the case of GIS tests, two dotted parts like "gis_tests.gdal_tests".
      """
      discovery_dirs = ['']
      if gis_enabled:
          # GIS tests are in nested apps
          discovery_dirs.append('gis_tests')
      else:
          SUBDIRS_TO_SKIP[''].add('gis_tests')
  
      for dirname in discovery_dirs:
          dirpath = os.path.join(RUNTESTS_DIR, dirname)
          subdirs_to_skip = SUBDIRS_TO_SKIP[dirname]
          with os.scandir(dirpath) as entries:
              for f in entries:
                  if (
                      '.' in f.name or
                      os.path.basename(f.name) in subdirs_to_skip or
                      f.is_file() or
                      not os.path.exists(os.path.join(f.path, '__init__.py'))
                  ):
                      continue
                  test_module = f.name
                  if dirname:
                      test_module = dirname + '.' + test_module
                  yield test_module
  
  
  def get_label_module(label):
      """Return the top-level module part for a test label."""
      path = Path(label)
      if len(path.parts) == 1:
          # Interpret the label as a dotted module name.
          return label.split('.')[0]
  
      # Otherwise, interpret the label as a path. Check existence first to
      # provide a better error message than relative_to() if it doesn't exist.
      if not path.exists():
          raise RuntimeError(f'Test label path {label} does not exist')
      path = path.resolve()
      rel_path = path.relative_to(RUNTESTS_DIR)
      return rel_path.parts[0]
  
  
  def get_filtered_test_modules(start_at, start_after, gis_enabled, test_labels=None):
      if test_labels is None:
          test_labels = []
      # Reduce each test label to just the top-level module part.
      label_modules = set()
      for label in test_labels:
          test_module = get_label_module(label)
          label_modules.add(test_module)
  
      # It would be nice to put this validation earlier but it must come after
      # django.setup() so that connection.features.gis_enabled can be accessed.
      if 'gis_tests' in label_modules and not gis_enabled:
          print('Aborting: A GIS database backend is required to run gis_tests.')
          sys.exit(1)
  
      def _module_match_label(module_name, label):
          # Exact or ancestor match.
          return module_name == label or module_name.startswith(label + '.')
  
      start_label = start_at or start_after
      for test_module in get_test_modules(gis_enabled):
          if start_label:
              if not _module_match_label(test_module, start_label):
                  continue
              start_label = ''
              if not start_at:
                  assert start_after
                  # Skip the current one before starting.
                  continue
          # If the module (or an ancestor) was named on the command line, or
          # no modules were named (i.e., run all), include the test module.
          if not test_labels or any(
              _module_match_label(test_module, label_module) for
              label_module in label_modules
          ):
              yield test_module
  
  
  def setup_collect_tests(start_at, start_after, test_labels=None):
      state = {
          'INSTALLED_APPS': settings.INSTALLED_APPS,
          'ROOT_URLCONF': getattr(settings, "ROOT_URLCONF", ""),
          'TEMPLATES': settings.TEMPLATES,
          'LANGUAGE_CODE': settings.LANGUAGE_CODE,
          'STATIC_URL': settings.STATIC_URL,
          'STATIC_ROOT': settings.STATIC_ROOT,
          'MIDDLEWARE': settings.MIDDLEWARE,
      }
  
      # Redirect some settings for the duration of these tests.
      settings.INSTALLED_APPS = ALWAYS_INSTALLED_APPS
      settings.ROOT_URLCONF = 'urls'
      settings.STATIC_URL = 'static/'
      settings.STATIC_ROOT = os.path.join(TMPDIR, 'static')
      settings.TEMPLATES = [{
          'BACKEND': 'django.template.backends.django.DjangoTemplates',
          'DIRS': [TEMPLATE_DIR],
          'APP_DIRS': True,
          'OPTIONS': {
              'context_processors': [
                  'django.template.context_processors.debug',
                  'django.template.context_processors.request',
                  'django.contrib.auth.context_processors.auth',
                  'django.contrib.messages.context_processors.messages',
              ],
          },
      }]
      settings.LANGUAGE_CODE = 'en'
      settings.SITE_ID = 1
      settings.MIDDLEWARE = ALWAYS_MIDDLEWARE
      settings.MIGRATION_MODULES = {
          # This lets us skip creating migrations for the test models as many of
          # them depend on one of the following contrib applications.
          'auth': None,
          'contenttypes': None,
          'sessions': None,
      }
      log_config = copy.deepcopy(DEFAULT_LOGGING)
      # Filter out non-error logging so we don't have to capture it in lots of
      # tests.
      log_config['loggers']['django']['level'] = 'ERROR'
      settings.LOGGING = log_config
      settings.SILENCED_SYSTEM_CHECKS = [
          'fields.W342',  # ForeignKey(unique=True) -> OneToOneField
      ]
  
      # Load all the ALWAYS_INSTALLED_APPS.
      django.setup()
  
      # This flag must be evaluated after django.setup() because otherwise it can
      # raise AppRegistryNotReady when running gis_tests in isolation on some
      # backends (e.g. PostGIS).
      gis_enabled = connection.features.gis_enabled
  
      test_modules = list(get_filtered_test_modules(
          start_at, start_after, gis_enabled, test_labels=test_labels,
      ))
      return test_modules, state
  
  
  def teardown_collect_tests(state):
      # Restore the old settings.
      for key, value in state.items():
          setattr(settings, key, value)
  
  
  def get_installed():
      return [app_config.name for app_config in apps.get_app_configs()]
  
  
  # This function should be called only after calling django.setup(),
  # since it calls connection.features.gis_enabled.
  def get_apps_to_install(test_modules):
      for test_module in test_modules:
          if test_module in CONTRIB_TESTS_TO_APPS:
              yield from CONTRIB_TESTS_TO_APPS[test_module]
          yield test_module
  
      # Add contrib.gis to INSTALLED_APPS if needed (rather than requiring
      # @override_settings(INSTALLED_APPS=...) on all test cases.
      if connection.features.gis_enabled:
          yield 'django.contrib.gis'
  
  
  def setup_run_tests(verbosity, start_at, start_after, test_labels=None):
      test_modules, state = setup_collect_tests(start_at, start_after, test_labels=test_labels)
  
      installed_apps = set(get_installed())
      for app in get_apps_to_install(test_modules):
          if app in installed_apps:
              continue
          if verbosity >= 2:
              print(f'Importing application {app}')
          settings.INSTALLED_APPS.append(app)
          installed_apps.add(app)
  
      apps.set_installed_apps(settings.INSTALLED_APPS)
  
      # Force declaring available_apps in TransactionTestCase for faster tests.
      def no_available_apps(self):
          raise Exception(
              'Please define available_apps in TransactionTestCase and its '
              'subclasses.'
          )
      TransactionTestCase.available_apps = property(no_available_apps)
      TestCase.available_apps = None
  
      # Set an environment variable that other code may consult to see if
      # Django's own test suite is running.
      os.environ['RUNNING_DJANGOS_TEST_SUITE'] = 'true'
  
      test_labels = test_labels or test_modules
      return test_labels, state
  
  
  def teardown_run_tests(state):
      teardown_collect_tests(state)
      # Discard the multiprocessing.util finalizer that tries to remove a
      # temporary directory that's already removed by this script's
      # atexit.register(shutil.rmtree, TMPDIR) handler. Prevents
      # FileNotFoundError at the end of a test run (#27890).
      from multiprocessing.util import _finalizer_registry
      _finalizer_registry.pop((-100, 0), None)
      del os.environ['RUNNING_DJANGOS_TEST_SUITE']
  
  
  class ActionSelenium(argparse.Action):
      """
      Validate the comma-separated list of requested browsers.
      """
      def __call__(self, parser, namespace, values, option_string=None):
          browsers = values.split(',')
          for browser in browsers:
              try:
                  SeleniumTestCaseBase.import_webdriver(browser)
              except ImportError:
                  raise argparse.ArgumentError(self, "Selenium browser specification '%s' is not valid." % browser)
          setattr(namespace, self.dest, browsers)
  
  
  def django_tests(verbosity, interactive, failfast, keepdb, reverse,
                   test_labels, debug_sql, parallel, tags, exclude_tags,
                   test_name_patterns, start_at, start_after, pdb, buffer,
                   timing, shuffle):
      if parallel in {0, 'auto'}:
          max_parallel = get_max_test_processes()
      else:
          max_parallel = parallel
  
      if verbosity >= 1:
          msg = "Testing against Django installed in '%s'" % os.path.dirname(django.__file__)
          if max_parallel > 1:
              msg += " with up to %d processes" % max_parallel
          print(msg)
  
      test_labels, state = setup_run_tests(verbosity, start_at, start_after, test_labels)
      # Run the test suite, including the extra validation tests.
      if not hasattr(settings, 'TEST_RUNNER'):
          settings.TEST_RUNNER = 'django.test.runner.DiscoverRunner'
  
      if parallel in {0, 'auto'}:
          # This doesn't work before django.setup() on some databases.
          if all(conn.features.can_clone_databases for conn in connections.all()):
              parallel = max_parallel
          else:
              parallel = 1
  
      TestRunner = get_runner(settings)
      test_runner = TestRunner(
          verbosity=verbosity,
          interactive=interactive,
          failfast=failfast,
          keepdb=keepdb,
          reverse=reverse,
          debug_sql=debug_sql,
          parallel=parallel,
          tags=tags,
          exclude_tags=exclude_tags,
          test_name_patterns=test_name_patterns,
          pdb=pdb,
          buffer=buffer,
          timing=timing,
          shuffle=shuffle,
      )
      failures = test_runner.run_tests(test_labels)
      teardown_run_tests(state)
      return failures
  
  
  def collect_test_modules(start_at, start_after):
      test_modules, state = setup_collect_tests(start_at, start_after)
      teardown_collect_tests(state)
      return test_modules
  
  
  def get_subprocess_args(options):
      subprocess_args = [
          sys.executable, __file__, '--settings=%s' % options.settings
      ]
      if options.failfast:
          subprocess_args.append('--failfast')
      if options.verbosity:
          subprocess_args.append('--verbosity=%s' % options.verbosity)
      if not options.interactive:
          subprocess_args.append('--noinput')
      if options.tags:
          subprocess_args.append('--tag=%s' % options.tags)
      if options.exclude_tags:
          subprocess_args.append('--exclude_tag=%s' % options.exclude_tags)
      if options.shuffle is not False:
          if options.shuffle is None:
              subprocess_args.append('--shuffle')
          else:
              subprocess_args.append('--shuffle=%s' % options.shuffle)
      return subprocess_args
  
  
  def bisect_tests(bisection_label, options, test_labels, start_at, start_after):
      if not test_labels:
          test_labels = collect_test_modules(start_at, start_after)
  
      print('***** Bisecting test suite: %s' % ' '.join(test_labels))
  
      # Make sure the bisection point isn't in the test list
      # Also remove tests that need to be run in specific combinations
      for label in [bisection_label, 'model_inheritance_same_model_name']:
          try:
              test_labels.remove(label)
          except ValueError:
              pass
  
      subprocess_args = get_subprocess_args(options)
  
      iteration = 1
      while len(test_labels) > 1:
          midpoint = len(test_labels) // 2
          test_labels_a = test_labels[:midpoint] + [bisection_label]
          test_labels_b = test_labels[midpoint:] + [bisection_label]
          print('***** Pass %da: Running the first half of the test suite' % iteration)
          print('***** Test labels: %s' % ' '.join(test_labels_a))
          failures_a = subprocess.run(subprocess_args + test_labels_a)
  
          print('***** Pass %db: Running the second half of the test suite' % iteration)
          print('***** Test labels: %s' % ' '.join(test_labels_b))
          print('')
          failures_b = subprocess.run(subprocess_args + test_labels_b)
  
          if failures_a.returncode and not failures_b.returncode:
              print("***** Problem found in first half. Bisecting again...")
              iteration += 1
              test_labels = test_labels_a[:-1]
          elif failures_b.returncode and not failures_a.returncode:
              print("***** Problem found in second half. Bisecting again...")
              iteration += 1
              test_labels = test_labels_b[:-1]
          elif failures_a.returncode and failures_b.returncode:
              print("***** Multiple sources of failure found")
              break
          else:
              print("***** No source of failure found... try pair execution (--pair)")
              break
  
      if len(test_labels) == 1:
          print("***** Source of error: %s" % test_labels[0])
  
  
  def paired_tests(paired_test, options, test_labels, start_at, start_after):
      if not test_labels:
          test_labels = collect_test_modules(start_at, start_after)
  
      print('***** Trying paired execution')
  
      # Make sure the constant member of the pair isn't in the test list
      # Also remove tests that need to be run in specific combinations
      for label in [paired_test, 'model_inheritance_same_model_name']:
          try:
              test_labels.remove(label)
          except ValueError:
              pass
  
      subprocess_args = get_subprocess_args(options)
  
      for i, label in enumerate(test_labels):
          print('***** %d of %d: Check test pairing with %s' % (
                i + 1, len(test_labels), label))
          failures = subprocess.call(subprocess_args + [label, paired_test])
          if failures:
              print('***** Found problem pair with %s' % label)
              return
  
      print('***** No problem pair found')
  
  
  if __name__ == "__main__":
      parser = argparse.ArgumentParser(description="Run the Django test suite.")
      parser.add_argument(
          'modules', nargs='*', metavar='module',
          help='Optional path(s) to test modules; e.g. "i18n" or '
               '"i18n.tests.TranslationTests.test_lazy_objects".',
      )
      parser.add_argument(
          '-v', '--verbosity', default=1, type=int, choices=[0, 1, 2, 3],
          help='Verbosity level; 0=minimal output, 1=normal output, 2=all output',
      )
      parser.add_argument(
          '--noinput', action='store_false', dest='interactive',
          help='Tells Django to NOT prompt the user for input of any kind.',
      )
      parser.add_argument(
          '--failfast', action='store_true',
          help='Tells Django to stop running the test suite after first failed test.',
      )
      parser.add_argument(
          '--keepdb', action='store_true',
          help='Tells Django to preserve the test database between runs.',
      )
      parser.add_argument(
          '--settings',
          help='Python path to settings module, e.g. "myproject.settings". If '
               'this isn\'t provided, either the DJANGO_SETTINGS_MODULE '
               'environment variable or "test_sqlite" will be used.',
      )
      parser.add_argument(
          '--bisect',
          help='Bisect the test suite to discover a test that causes a test '
               'failure when combined with the named test.',
      )
      parser.add_argument(
          '--pair',
          help='Run the test suite in pairs with the named test to find problem pairs.',
      )
      parser.add_argument(
          '--shuffle', nargs='?', default=False, type=int, metavar='SEED',
          help=(
              'Shuffle the order of test cases to help check that tests are '
              'properly isolated.'
          ),
      )
      parser.add_argument(
          '--reverse', action='store_true',
          help='Sort test suites and test cases in opposite order to debug '
               'test side effects not apparent with normal execution lineup.',
      )
      parser.add_argument(
          '--selenium', action=ActionSelenium, metavar='BROWSERS',
          help='A comma-separated list of browsers to run the Selenium tests against.',
      )
      parser.add_argument(
          '--headless', action='store_true',
          help='Run selenium tests in headless mode, if the browser supports the option.',
      )
      parser.add_argument(
          '--selenium-hub',
          help='A URL for a selenium hub instance to use in combination with --selenium.',
      )
      parser.add_argument(
          '--external-host', default=socket.gethostname(),
          help='The external host that can be reached by the selenium hub instance when running Selenium '
               'tests via Selenium Hub.',
      )
      parser.add_argument(
          '--debug-sql', action='store_true',
          help='Turn on the SQL query logger within tests.',
      )
      # 0 is converted to "auto" or 1 later on, depending on a method used by
      # multiprocessing to start subprocesses and on the backend support for
      # cloning databases.
      parser.add_argument(
          '--parallel', nargs='?', const='auto', default=0,
          type=parallel_type, metavar='N',
          help=(
              'Run tests using up to N parallel processes. Use the value "auto" '
              'to run one test process for each processor core.'
          ),
      )
      parser.add_argument(
          '--tag', dest='tags', action='append',
          help='Run only tests with the specified tags. Can be used multiple times.',
      )
      parser.add_argument(
          '--exclude-tag', dest='exclude_tags', action='append',
          help='Do not run tests with the specified tag. Can be used multiple times.',
      )
      parser.add_argument(
          '--start-after', dest='start_after',
          help='Run tests starting after the specified top-level module.',
      )
      parser.add_argument(
          '--start-at', dest='start_at',
          help='Run tests starting at the specified top-level module.',
      )
      parser.add_argument(
          '--pdb', action='store_true',
          help='Runs the PDB debugger on error or failure.'
      )
      parser.add_argument(
          '-b', '--buffer', action='store_true',
          help='Discard output of passing tests.',
      )
      parser.add_argument(
          '--timing', action='store_true',
          help='Output timings, including database set up and total run time.',
      )
      parser.add_argument(
          '-k', dest='test_name_patterns', action='append',
          help=(
              'Only run test methods and classes matching test name pattern. '
              'Same as unittest -k option. Can be used multiple times.'
          ),
      )
  
      options = parser.parse_args()
  
      using_selenium_hub = options.selenium and options.selenium_hub
      if options.selenium_hub and not options.selenium:
          parser.error('--selenium-hub and --external-host require --selenium to be used.')
      if using_selenium_hub and not options.external_host:
          parser.error('--selenium-hub and --external-host must be used together.')
  
      # Allow including a trailing slash on app_labels for tab completion convenience
      options.modules = [os.path.normpath(labels) for labels in options.modules]
  
      mutually_exclusive_options = [options.start_at, options.start_after, options.modules]
      enabled_module_options = [bool(option) for option in mutually_exclusive_options].count(True)
      if enabled_module_options > 1:
          print('Aborting: --start-at, --start-after, and test labels are mutually exclusive.')
          sys.exit(1)
      for opt_name in ['start_at', 'start_after']:
          opt_val = getattr(options, opt_name)
          if opt_val:
              if '.' in opt_val:
                  print('Aborting: --%s must be a top-level module.' % opt_name.replace('_', '-'))
                  sys.exit(1)
              setattr(options, opt_name, os.path.normpath(opt_val))
      if options.settings:
          os.environ['DJANGO_SETTINGS_MODULE'] = options.settings
      else:
          os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'test_sqlite')
          options.settings = os.environ['DJANGO_SETTINGS_MODULE']
  
      if options.selenium:
          if not options.tags:
              options.tags = ['selenium']
          elif 'selenium' not in options.tags:
              options.tags.append('selenium')
          if options.selenium_hub:
              SeleniumTestCaseBase.selenium_hub = options.selenium_hub
              SeleniumTestCaseBase.external_host = options.external_host
          SeleniumTestCaseBase.headless = options.headless
          SeleniumTestCaseBase.browsers = options.selenium
  
      if options.bisect:
          bisect_tests(
              options.bisect, options, options.modules, options.start_at,
              options.start_after,
          )
      elif options.pair:
          paired_tests(
              options.pair, options, options.modules, options.start_at,
              options.start_after,
          )
      else:
          time_keeper = TimeKeeper() if options.timing else NullTimeKeeper()
          with time_keeper.timed('Total run'):
              failures = django_tests(
                  options.verbosity, options.interactive, options.failfast,
                  options.keepdb, options.reverse, options.modules,
                  options.debug_sql, options.parallel, options.tags,
                  options.exclude_tags,
                  getattr(options, 'test_name_patterns', None),
                  options.start_at, options.start_after, options.pdb, options.buffer,
                  options.timing, options.shuffle,
              )
          time_keeper.print_results()
          if failures:
              sys.exit(1)
  