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, 4 insertions, 8 deletions

diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index 8dd6ea6..44cf523 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -9,6 +9,7 @@ import os
 import errno
 import threading
 
+import unittest
 from unittest import TestCase, skipUnless
 from test import support as test_support
 from test.support import hashlib_helper
@@ -538,15 +539,10 @@ class TestTimeouts(TestCase):
             poplib.POP3(HOST, self.port, timeout=0)
 
 
-def test_main():
-    tests = [TestPOP3Class, TestTimeouts,
-             TestPOP3_SSLClass, TestPOP3_TLSClass]
+def setUpModule():
     thread_info = threading_helper.threading_setup()
-    try:
-        test_support.run_unittest(*tests)
-    finally:
-        threading_helper.threading_cleanup(*thread_info)
+    unittest.addModuleCleanup(threading_helper.threading_cleanup, *thread_info)
 
 
 if __name__ == '__main__':
-    test_main()
+    unittest.main()