From 606fc352799e372928fa2c978ab99f0fb6d6017c Mon Sep 17 00:00:00 2001
From: Adam Zapletal <adamzap@gmail.com>
Date: Sat, 18 Jan 2025 16:22:10 -0600
Subject: [PATCH] Fixed #36083 -- Ran system checks in ParallelTestSuite
 workers.

Workers created by ParallelTestSuite were not running system
checks in the spawn multiprocessing mode. In general this is
fine, but system checks can have side effects expected by tests.

This patch runs system checks inside of _init_worker, which is
only called by ParallelTestSuite.
---
 django/test/runner.py              | 5 ++++-
 tests/test_runner/models.py        | 7 +++++++
 tests/test_runner/test_parallel.py | 5 +++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/django/test/runner.py b/django/test/runner.py
index 1bfeca03af..8902dea3e0 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -439,7 +439,7 @@ def _init_worker(
     used_aliases=None,
 ):
     """
-    Switch to databases dedicated to this worker.
+    Switch to databases dedicated to this worker and run system checks.
 
     This helper lives at module-level because of the multiprocessing module's
     requirements.
@@ -463,6 +463,9 @@ def _init_worker(
             process_setup(*process_setup_args)
         django.setup()
         setup_test_environment(debug=debug_mode)
+        call_command(
+            "check", stdout=io.StringIO(), stderr=io.StringIO(), databases=used_aliases
+        )
 
     db_aliases = used_aliases if used_aliases is not None else connections
     for alias in db_aliases:
diff --git a/tests/test_runner/models.py b/tests/test_runner/models.py
index 80bf8dd8c7..54ec5e2b3d 100644
--- a/tests/test_runner/models.py
+++ b/tests/test_runner/models.py
@@ -6,6 +6,13 @@ class Person(models.Model):
     last_name = models.CharField(max_length=20)
     friends = models.ManyToManyField("self")
 
+    system_check_run_count = 0
+
+    @classmethod
+    def check(cls, *args, **kwargs):
+        cls.system_check_run_count += 1
+        return super().check(**kwargs)
+
 
 # A set of models that use a non-abstract inherited 'through' model.
 class ThroughBase(models.Model):
diff --git a/tests/test_runner/test_parallel.py b/tests/test_runner/test_parallel.py
index 3af0fbf2f9..f344f1a2db 100644
--- a/tests/test_runner/test_parallel.py
+++ b/tests/test_runner/test_parallel.py
@@ -8,6 +8,8 @@ from unittest.suite import TestSuite, _ErrorHolder
 from django.test import SimpleTestCase
 from django.test.runner import ParallelTestSuite, RemoteTestResult
 
+from . import models
+
 try:
     import tblib.pickling_support
 except ImportError:
@@ -48,6 +50,9 @@ class ParallelTestRunnerTest(SimpleTestCase):
             with self.subTest(index=i):
                 self.assertEqual(i, i)
 
+    def test_system_checks(self):
+        self.assertEqual(models.Person.system_check_run_count, 1)
+
 
 class SampleFailingSubtest(SimpleTestCase):
     # This method name doesn't begin with "test" to prevent test discovery