Refs #31621 -- Fixed handling --parallel option in test management command and runtests.py.

Regression in ae89daf46f83a7b39d599d289624c3377bfa4ab1.
Thanks Tim Graham for the report.

2 files changed, 32 insertions, 14 deletions

diff --git a/tests/test_runner/test_discover_runner.py b/tests/test_runner/test_discover_runner.py
index b73c1581e3..625de94067 100644
--- a/tests/test_runner/test_discover_runner.py
+++ b/tests/test_runner/test_discover_runner.py
@@ -9,7 +9,7 @@ from unittest import TestSuite, TextTestRunner, defaultTestLoader, mock
 
 from django.db import connections
 from django.test import SimpleTestCase
-from django.test.runner import DiscoverRunner
+from django.test.runner import DiscoverRunner, get_max_test_processes
 from django.test.utils import (
     NullTimeKeeper, TimeKeeper, captured_stderr, captured_stdout,
 )
@@ -54,11 +54,11 @@ class DiscoverRunnerParallelArgumentTests(SimpleTestCase):
 
     def test_parallel_flag(self, *mocked_objects):
         result = self.get_parser().parse_args(['--parallel'])
-        self.assertEqual(result.parallel, 12)
+        self.assertEqual(result.parallel, 'auto')
 
     def test_parallel_auto(self, *mocked_objects):
         result = self.get_parser().parse_args(['--parallel', 'auto'])
-        self.assertEqual(result.parallel, 12)
+        self.assertEqual(result.parallel, 'auto')
 
     def test_parallel_count(self, *mocked_objects):
         result = self.get_parser().parse_args(['--parallel', '17'])
@@ -70,20 +70,20 @@ class DiscoverRunnerParallelArgumentTests(SimpleTestCase):
         msg = "argument --parallel: 'unaccepted' is not an integer or the string 'auto'"
         self.assertIn(msg, stderr.getvalue())
 
-    @mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': '7'})
-    def test_parallel_env_var(self, *mocked_objects):
-        result = self.get_parser().parse_args([])
-        self.assertEqual(result.parallel, 7)
+    def test_get_max_test_processes(self, *mocked_objects):
+        self.assertEqual(get_max_test_processes(), 12)
 
-    @mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': 'typo'})
-    def test_parallel_env_var_non_int(self, *mocked_objects):
-        with self.assertRaises(ValueError):
-            self.get_parser().parse_args([])
+    @mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': '7'})
+    def test_get_max_test_processes_env_var(self, *mocked_objects):
+        self.assertEqual(get_max_test_processes(), 7)
 
-    def test_parallel_spawn(self, mocked_get_start_method, mocked_cpu_count):
+    def test_get_max_test_processes_spawn(
+        self, mocked_get_start_method, mocked_cpu_count,
+    ):
         mocked_get_start_method.return_value = 'spawn'
-        result = self.get_parser().parse_args(['--parallel'])
-        self.assertEqual(result.parallel, 1)
+        self.assertEqual(get_max_test_processes(), 1)
+        with mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': '7'}):
+            self.assertEqual(get_max_test_processes(), 1)
 
 
 class DiscoverRunnerTests(SimpleTestCase):
diff --git a/tests/test_runner/tests.py b/tests/test_runner/tests.py
index 485a35be9c..62b489abc7 100644
--- a/tests/test_runner/tests.py
+++ b/tests/test_runner/tests.py
@@ -434,6 +434,12 @@ class ManageCommandParallelTests(SimpleTestCase):
             )
         self.assertEqual(stderr.getvalue(), '')
 
+    @mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': '7'})
+    def test_no_parallel_django_test_processes_env(self, *mocked_objects):
+        with captured_stderr() as stderr:
+            call_command('test', testrunner='test_runner.tests.MockTestRunner')
+        self.assertEqual(stderr.getvalue(), '')
+
     @mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': 'invalid'})
     def test_django_test_processes_env_non_int(self, *mocked_objects):
         with self.assertRaises(ValueError):
@@ -443,6 +449,18 @@ class ManageCommandParallelTests(SimpleTestCase):
                 testrunner='test_runner.tests.MockTestRunner',
             )
 
+    @mock.patch.dict(os.environ, {'DJANGO_TEST_PROCESSES': '7'})
+    def test_django_test_processes_parallel_default(self, *mocked_objects):
+        for parallel in ['--parallel', '--parallel=auto']:
+            with self.subTest(parallel=parallel):
+                with captured_stderr() as stderr:
+                    call_command(
+                        'test',
+                        parallel,
+                        testrunner='test_runner.tests.MockTestRunner',
+                    )
+                self.assertIn('parallel=7', stderr.getvalue())
+
 
 class CustomTestRunnerOptionsSettingsTests(AdminScriptTestCase):
     """