bpo-41966: Fix pickling pure datetime.time subclasses (GH-22731)

diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 8b61c26..775d315 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1781,6 +1781,7 @@
             green = pickler.dumps(orig, proto)
             derived = unpickler.loads(green)
             self.assertEqual(orig, derived)
+            self.assertTrue(isinstance(derived, SubclassDate))
 
     def test_backdoor_resistance(self):
         # For fast unpickling, the constructor accepts a pickle byte string.
@@ -2308,6 +2309,7 @@
             green = pickler.dumps(orig, proto)
             derived = unpickler.loads(green)
             self.assertEqual(orig, derived)
+            self.assertTrue(isinstance(derived, SubclassDatetime))
 
     def test_compat_unpickle(self):
         tests = [
@@ -3357,6 +3359,7 @@
             green = pickler.dumps(orig, proto)
             derived = unpickler.loads(green)
             self.assertEqual(orig, derived)
+            self.assertTrue(isinstance(derived, SubclassTime))
 
     def test_compat_unpickle(self):
         tests = [