[3.13] GH-120097: Make FrameLocalsProxy a mapping (GH-120101) (GH-120749)

Co-authored-by: Alyssa Coghlan <ncoghlan@gmail.com>

Lib/test/test_frame.py

@@ -13,6 +13,7 @@ try:
 except ImportError:
     _testcapi = None
 
+from collections.abc import Mapping
 from test import support
 from test.support import import_helper, threading_helper, Py_GIL_DISABLED
 from test.support.script_helper import assert_python_ok
@@ -421,6 +422,17 @@ class TestFrameLocals(unittest.TestCase):
         with self.assertRaises(TypeError):
             copy.deepcopy(d)
 
+    def test_is_mapping(self):
+        x = 1
+        d = sys._getframe().f_locals
+        self.assertIsInstance(d, Mapping)
+        match d:
+            case {"x": value}:
+                self.assertEqual(value, 1)
+                kind = "mapping"
+            case _:
+                kind = "other"
+        self.assertEqual(kind, "mapping")
 
     def _x_stringlikes(self):
         class StringSubclass(str):