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, 8 insertions, 6 deletions

diff --git a/Lib/test/test_global.py b/Lib/test/test_global.py
index c71d055297..d0bde3fd04 100644
--- a/Lib/test/test_global.py
+++ b/Lib/test/test_global.py
@@ -1,6 +1,6 @@
 """Verify that warnings are issued for global statements following use."""
 
-from test.support import run_unittest, check_syntax_error
+from test.support import check_syntax_error
 from test.support.warnings_helper import check_warnings
 import unittest
 import warnings
@@ -53,10 +53,12 @@ x = 2
         compile(prog_text_4, "<test string>", "exec")
 
 
-def test_main():
-    with warnings.catch_warnings():
-        warnings.filterwarnings("error", module="<test string>")
-        run_unittest(GlobalTests)
+def setUpModule():
+    cm = warnings.catch_warnings()
+    cm.__enter__()
+    unittest.addModuleCleanup(cm.__exit__, None, None, None)
+    warnings.filterwarnings("error", module="<test string>")
+
 
 if __name__ == "__main__":
-    test_main()
+    unittest.main()