#17346: make sure pickle tests are run against all protocols.

Lib/test/pickletester.py

@@ -503,10 +503,10 @@ class AbstractPickleTests(unittest.TestCase):
         i = C()
         i.attr = i
         for proto in protocols:
-            s = self.dumps(i, 2)
+            s = self.dumps(i, proto)
             x = self.loads(s)
             self.assertEqual(dir(x), dir(i))
-            self.assertTrue(x.attr is x)
+            self.assertIs(x.attr, x)
 
     def test_recursive_multi(self):
         l = []