bpo-46386: improve `test_typing:test_immutability_by_copy_and_pickle` (GH-30613)

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index cf719df6da1d7a0e7177ffe1e2f3a84d1f3f5b87..c8a077e2f1ff553bb2bf3bc0cbae73f989145b0b 100644 (file)
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -2130,22 +2130,30 @@ class GenericTests(BaseTestCase):
     def test_immutability_by_copy_and_pickle(self):
         # Special forms like Union, Any, etc., generic aliases to containers like List,
         # Mapping, etc., and type variabcles are considered immutable by copy and pickle.
-        global TP, TPB, TPV  # for pickle
+        global TP, TPB, TPV, PP  # for pickle
         TP = TypeVar('TP')
         TPB = TypeVar('TPB', bound=int)
         TPV = TypeVar('TPV', bytes, str)
-        for X in [TP, TPB, TPV, List, typing.Mapping, ClassVar, typing.Iterable,
+        PP = ParamSpec('PP')
+        for X in [TP, TPB, TPV, PP,
+                  List, typing.Mapping, ClassVar, typing.Iterable,
                   Union, Any, Tuple, Callable]:
-            self.assertIs(copy(X), X)
-            self.assertIs(deepcopy(X), X)
-            self.assertIs(pickle.loads(pickle.dumps(X)), X)
+            with self.subTest(thing=X):
+                self.assertIs(copy(X), X)
+                self.assertIs(deepcopy(X), X)
+                for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+                    self.assertIs(pickle.loads(pickle.dumps(X, proto)), X)
+        del TP, TPB, TPV, PP
+
         # Check that local type variables are copyable.
         TL = TypeVar('TL')
         TLB = TypeVar('TLB', bound=int)
         TLV = TypeVar('TLV', bytes, str)
-        for X in [TL, TLB, TLV]:
-            self.assertIs(copy(X), X)
-            self.assertIs(deepcopy(X), X)
+        PL = ParamSpec('PL')
+        for X in [TL, TLB, TLV, PL]:
+            with self.subTest(thing=X):
+                self.assertIs(copy(X), X)
+                self.assertIs(deepcopy(X), X)
 
     def test_copy_generic_instances(self):
         T = TypeVar('T')