Fixed #32591 -- Made DiscoverRunner order _FailedTest objects first.

Failures detected when loading tests are ordered before all of the
above for quicker feedback. This includes things like test modules that
couldn't be found or that couldn't be loaded due to syntax errors.

django/test/runner.py

@@ -635,7 +635,11 @@ class DiscoverRunner:
                     print('Excluding test tag(s): %s.' % ', '.join(sorted(self.exclude_tags)))
             all_tests = filter_tests_by_tags(all_tests, self.tags, self.exclude_tags)
 
-        all_tests = reorder_tests(all_tests, self.reorder_by, self.reverse)
+        # Put the failures detected at load time first for quicker feedback.
+        # _FailedTest objects include things like test modules that couldn't be
+        # found or that couldn't be loaded due to syntax errors.
+        test_types = (unittest.loader._FailedTest, *self.reorder_by)
+        all_tests = reorder_tests(all_tests, test_types, self.reverse)
         suite = self.test_suite(all_tests)
 
         if self.parallel > 1:

docs/topics/testing/overview.txt

@@ -229,10 +229,21 @@ the Django test runner reorders tests in the following way:
     database by a given :class:`~django.test.TransactionTestCase` test, they
     must be updated to be able to run independently.
 
+.. note::
+
+    Failures detected when loading tests are ordered before all of the above
+    for quicker feedback. This includes things like test modules that couldn't
+    be found or that couldn't be loaded due to syntax errors.
+
 You may reverse the execution order inside groups using the :option:`test
 --reverse` option. This can help with ensuring your tests are independent from
 each other.
 
+.. versionchanged:: 4.0
+
+    In older versions, failures detected when loading tests were not ordered
+    first.
+
 .. _test-case-serialized-rollback:
 
 Rollback emulation

tests/test_runner/test_discover_runner.py

@@ -1,4 +1,5 @@
 import os
+import unittest.loader
 from argparse import ArgumentParser
 from contextlib import contextmanager
 from unittest import TestSuite, TextTestRunner, defaultTestLoader, mock
@@ -209,6 +210,15 @@ class DiscoverRunnerTests(SimpleTestCase):
         self.assertIn('test_2', suite[9].id(),
                       msg="Methods of unittest cases should be reversed.")
 
+    def test_build_suite_failed_tests_first(self):
+        # The "doesnotexist" label results in a _FailedTest instance.
+        suite = DiscoverRunner().build_suite(
+            test_labels=['test_runner_apps.sample', 'doesnotexist'],
+        )
+        tests = list(suite)
+        self.assertIsInstance(tests[0], unittest.loader._FailedTest)
+        self.assertNotIsInstance(tests[-1], unittest.loader._FailedTest)
+
     def test_overridable_get_test_runner_kwargs(self):
         self.assertIsInstance(DiscoverRunner().get_test_runner_kwargs(), dict)