Issue #22777: Test pickling with all protocols.
diff --git a/Lib/test/test_sets.py b/Lib/test/test_sets.py
index 319bdcb..0a89908 100644
--- a/Lib/test/test_sets.py
+++ b/Lib/test/test_sets.py
@@ -75,10 +75,11 @@
             self.assertIn(v, self.values)
 
     def test_pickling(self):
-        p = pickle.dumps(self.set)
-        copy = pickle.loads(p)
-        self.assertEqual(self.set, copy,
-                         "%s != %s" % (self.set, copy))
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            p = pickle.dumps(self.set, proto)
+            copy = pickle.loads(p)
+            self.assertEqual(self.set, copy,
+                             "%s != %s" % (self.set, copy))
 
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