bpo-45229: Remove test_main in many tests (GH-28405)

Instead of explicitly enumerate test classes for run_unittest()
use the unittest ability to discover tests. This also makes these
tests discoverable and runnable with unittest.

load_tests() can be used for dynamic generating tests and adding
doctests. setUpModule(), tearDownModule() and addModuleCleanup()
can be used for running code before and after all module tests.

1 files changed, 7 insertions, 10 deletions

diff --git a/Lib/test/test_importlib/test_threaded_import.py b/Lib/test/test_importlib/test_threaded_import.py
index 03bde96..76b028e 100644
--- a/Lib/test/test_importlib/test_threaded_import.py
+++ b/Lib/test/test_importlib/test_threaded_import.py
@@ -14,7 +14,7 @@ import shutil
 import threading
 import unittest
 from unittest import mock
-from test.support import (verbose, run_unittest)
+from test.support import verbose
 from test.support.import_helper import forget
 from test.support.os_helper import (TESTFN, unlink, rmtree)
 from test.support import script_helper, threading_helper
@@ -258,19 +258,16 @@ class ThreadedImportTests(unittest.TestCase):
         script_helper.assert_python_ok(fn)
 
 
-@threading_helper.reap_threads
-def test_main():
-    old_switchinterval = None
+def setUpModule():
+    thread_info = threading_helper.threading_setup()
+    unittest.addModuleCleanup(threading_helper.threading_cleanup, *thread_info)
     try:
         old_switchinterval = sys.getswitchinterval()
+        unittest.addModuleCleanup(sys.setswitchinterval, old_switchinterval)
         sys.setswitchinterval(1e-5)
     except AttributeError:
         pass
-    try:
-        run_unittest(ThreadedImportTests)
-    finally:
-        if old_switchinterval is not None:
-            sys.setswitchinterval(old_switchinterval)
+
 
 if __name__ == "__main__":
-    test_main()
+    unittets.main()