gh-103724: Add test case if no arg as provided in os.register_at_fork (gh-103725)

Author: itsankitkp

Lib/test/test_posix.py

@@ -231,6 +231,9 @@ def test_register_at_fork(self):
         with self.assertRaises(TypeError, msg="Invalid arg was allowed"):
             # Ensure a combination of valid and invalid is an error.
             os.register_at_fork(before=None, after_in_parent=lambda: 3)
+        with self.assertRaises(TypeError, msg="At least one argument is required"):
+            # when no arg is passed
+            os.register_at_fork()
         with self.assertRaises(TypeError, msg="Invalid arg was allowed"):
             # Ensure a combination of valid and invalid is an error.
             os.register_at_fork(before=lambda: None, after_in_child='')