Fixed #31169 -- Adapted the parallel test runner to use spawn.

Co-authored-by: Valz <ahmadahussein0@gmail.com>
Co-authored-by: Nick Pope <nick@nickpope.me.uk>

tests/admin_checks/tests.py

@@ -70,6 +70,8 @@ class SessionMiddlewareSubclass(SessionMiddleware):
     ],
 )
 class SystemChecksTestCase(SimpleTestCase):
+    databases = "__all__"
+
     def test_checks_are_performed(self):
         admin.site.register(Song, MyAdmin)
         try:

tests/backends/sqlite/test_creation.py

@@ -1,7 +1,9 @@
 import copy
+import multiprocessing
 import unittest
+from unittest import mock
 
-from django.db import DEFAULT_DB_ALIAS, connection, connections
+from django.db import DEFAULT_DB_ALIAS, NotSupportedError, connection, connections
 from django.test import SimpleTestCase
 
 
@@ -33,3 +35,9 @@ class TestDbSignatureTests(SimpleTestCase):
                 creation_class = test_connection.creation_class(test_connection)
                 clone_settings_dict = creation_class.get_test_db_clone_settings("1")
                 self.assertEqual(clone_settings_dict["NAME"], expected_clone_name)
+
+    @mock.patch.object(multiprocessing, "get_start_method", return_value="forkserver")
+    def test_get_test_db_clone_settings_not_supported(self, *mocked_objects):
+        msg = "Cloning with start method 'forkserver' is not supported."
+        with self.assertRaisesMessage(NotSupportedError, msg):
+            connection.creation.get_test_db_clone_settings(1)

tests/check_framework/tests.py

@@ -362,5 +362,7 @@ class CheckFrameworkReservedNamesTests(SimpleTestCase):
 
 
 class ChecksRunDuringTests(SimpleTestCase):
+    databases = "__all__"
+
     def test_registered_check_did_run(self):
         self.assertTrue(my_check.did_run)

tests/contenttypes_tests/test_checks.py

@@ -11,6 +11,8 @@ from django.test.utils import isolate_apps
 
 @isolate_apps("contenttypes_tests", attr_name="apps")
 class GenericForeignKeyTests(SimpleTestCase):
+    databases = "__all__"
+
     def test_missing_content_type_field(self):
         class TaggedItem(models.Model):
             # no content_type field

tests/contenttypes_tests/test_management.py

@@ -22,6 +22,13 @@ class RemoveStaleContentTypesTests(TestCase):
 
     @classmethod
     def setUpTestData(cls):
+        with captured_stdout():
+            call_command(
+                "remove_stale_contenttypes",
+                interactive=False,
+                include_stale_apps=True,
+                verbosity=2,
+            )
         cls.before_count = ContentType.objects.count()
         cls.content_type = ContentType.objects.create(
             app_label="contenttypes_tests", model="Fake"

tests/postgres_tests/test_bulk_update.py

@@ -1,5 +1,7 @@
 from datetime import date
 
+from django.test import modify_settings
+
 from . import PostgreSQLTestCase
 from .models import (
     HStoreModel,
@@ -16,6 +18,7 @@ except ImportError:
     pass  # psycopg2 isn't installed.
 
 
+@modify_settings(INSTALLED_APPS={"append": "django.contrib.postgres"})
 class BulkSaveTests(PostgreSQLTestCase):
     def test_bulk_update(self):
         test_data = [

tests/runtests.py

@@ -3,6 +3,7 @@ import argparse
 import atexit
 import copy
 import gc
+import multiprocessing
 import os
 import shutil
 import socket
@@ -10,6 +11,7 @@ import subprocess
 import sys
 import tempfile
 import warnings
+from functools import partial
 from pathlib import Path
 
 try:
@@ -24,7 +26,7 @@ else:
     from django.core.exceptions import ImproperlyConfigured
     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.runner import _init_worker, 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
@@ -382,7 +384,8 @@ def django_tests(
             msg += " with up to %d processes" % max_parallel
         print(msg)
 
-    test_labels, state = setup_run_tests(verbosity, start_at, start_after, test_labels)
+    process_setup_args = (verbosity, start_at, start_after, test_labels)
+    test_labels, state = setup_run_tests(*process_setup_args)
     # Run the test suite, including the extra validation tests.
     if not hasattr(settings, "TEST_RUNNER"):
         settings.TEST_RUNNER = "django.test.runner.DiscoverRunner"
@@ -395,6 +398,11 @@ def django_tests(
             parallel = 1
 
     TestRunner = get_runner(settings)
+    TestRunner.parallel_test_suite.init_worker = partial(
+        _init_worker,
+        process_setup=setup_run_tests,
+        process_setup_args=process_setup_args,
+    )
     test_runner = TestRunner(
         verbosity=verbosity,
         interactive=interactive,
@@ -718,6 +726,11 @@ if __name__ == "__main__":
         options.settings = os.environ["DJANGO_SETTINGS_MODULE"]
 
     if options.selenium:
+        if multiprocessing.get_start_method() == "spawn" and options.parallel != 1:
+            parser.error(
+                "You cannot use --selenium with parallel tests on this system. "
+                "Pass --parallel=1 to use --selenium."
+            )
         if not options.tags:
             options.tags = ["selenium"]
         elif "selenium" not in options.tags:

tests/test_runner/test_discover_runner.py

@@ -86,6 +86,16 @@ class DiscoverRunnerParallelArgumentTests(SimpleTestCase):
         mocked_cpu_count,
     ):
         mocked_get_start_method.return_value = "spawn"
+        self.assertEqual(get_max_test_processes(), 12)
+        with mock.patch.dict(os.environ, {"DJANGO_TEST_PROCESSES": "7"}):
+            self.assertEqual(get_max_test_processes(), 7)
+
+    def test_get_max_test_processes_forkserver(
+        self,
+        mocked_get_start_method,
+        mocked_cpu_count,
+    ):
+        mocked_get_start_method.return_value = "forkserver"
         self.assertEqual(get_max_test_processes(), 1)
         with mock.patch.dict(os.environ, {"DJANGO_TEST_PROCESSES": "7"}):
             self.assertEqual(get_max_test_processes(), 1)

tests/test_runner/tests.py

@@ -480,8 +480,6 @@ class ManageCommandTests(unittest.TestCase):
 # Isolate from the real environment.
 @mock.patch.dict(os.environ, {}, clear=True)
 @mock.patch.object(multiprocessing, "cpu_count", return_value=12)
-# Python 3.8 on macOS defaults to 'spawn' mode.
-@mock.patch.object(multiprocessing, "get_start_method", return_value="fork")
 class ManageCommandParallelTests(SimpleTestCase):
     def test_parallel_default(self, *mocked_objects):
         with captured_stderr() as stderr:
@@ -507,8 +505,8 @@ class ManageCommandParallelTests(SimpleTestCase):
         # Parallel is disabled by default.
         self.assertEqual(stderr.getvalue(), "")
 
-    def test_parallel_spawn(self, mocked_get_start_method, mocked_cpu_count):
-        mocked_get_start_method.return_value = "spawn"
+    @mock.patch.object(multiprocessing, "get_start_method", return_value="spawn")
+    def test_parallel_spawn(self, *mocked_objects):
         with captured_stderr() as stderr:
             call_command(
                 "test",
@@ -517,8 +515,8 @@ class ManageCommandParallelTests(SimpleTestCase):
             )
         self.assertIn("parallel=1", stderr.getvalue())
 
-    def test_no_parallel_spawn(self, mocked_get_start_method, mocked_cpu_count):
-        mocked_get_start_method.return_value = "spawn"
+    @mock.patch.object(multiprocessing, "get_start_method", return_value="spawn")
+    def test_no_parallel_spawn(self, *mocked_objects):
         with captured_stderr() as stderr:
             call_command(
                 "test",