gh-131290: ensure that test files can be executed as standalone scripts

Lib/test/test_metaclass.py

@@ -297,4 +297,6 @@ def load_tests(loader, tests, pattern):
 
 
 if __name__ == "__main__":
+    # set __name__ to match doctest expectations
+    __name__ = "test.test_metaclass"
     unittest.main()

Lib/test/test_pyclbr.py

@@ -142,6 +142,12 @@ def defined_in(item, module):
                     self.assertHaskey(dict, name, ignore)
 
     def test_easy(self):
+        import importlib.util
+        if getattr(sys.modules["__main__"], "__spec__", None) is None:
+            sys.modules["__main__"].__spec__ = importlib.machinery.ModuleSpec(
+                name="__main__", loader=None, origin="built-in"
+            )
+
         self.checkModule('pyclbr')
         # XXX: Metaclasses are not supported
         # self.checkModule('ast')
@@ -214,6 +220,18 @@ def compare(parent1, children1, parent2, children2):
 
         compare(None, actual, None, expected)
 
+    def test_pdb_module(self):
+        import importlib.util
+        if getattr(sys.modules["__main__"], "__spec__", None) is None:
+            sys.modules["__main__"].__spec__ = importlib.machinery.ModuleSpec(
+                name="__main__", loader=None, origin="builtin"
+            )
+
+        self.checkModule(
+            'pdb',
+            ignore=('_ModuleTarget', '_ScriptTarget', '_ZipTarget', 'Pdb'),
+        )
+
     def test_others(self):
         cm = self.checkModule
 
@@ -223,11 +241,6 @@ def test_others(self):
         with warnings.catch_warnings():
             warnings.simplefilter('ignore', DeprecationWarning)
             cm('sre_parse', ignore=('dump', 'groups', 'pos')) # from sre_constants import *; property
-        cm(
-            'pdb',
-            # pyclbr does not handle elegantly `typing` or properties
-            ignore=('Union', '_ModuleTarget', '_ScriptTarget', '_ZipTarget', 'curframe_locals'),
-        )
         cm('pydoc', ignore=('input', 'output',)) # properties
 
         # Tests for modules inside packages

Lib/test/test_regrtest.py

@@ -2546,4 +2546,5 @@ def test_test_result_get_state(self):
 
 
 if __name__ == '__main__':
+    setup.setup_process()
     unittest.main()

Misc/NEWS.d/next/Tests/2025-03-17-19-47-27.gh-issue-131290.NyCIXR.rst

@@ -0,0 +1 @@
+# Several tests are modified when called directly via ./python Lib/test/...

Misc/NEWS.d/next/Tests/2025-04-07-13-45-23.gh-issue-131290.MaximGit1.rst

@@ -0,0 +1,3 @@
+Tests in :file:`Lib/test` can now be correctly executed as standalone scripts.
+
+Several tests were modified to correctly handle execution when called directly via `./python Lib/test/...`, ensuring that the `__spec__` attribute is properly set in certain modules like `__main__`.