Use Py_CLEAR().  Add unrelated test.
diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 01dded6..aab0c57 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -23,6 +23,9 @@
         self.s = self.thetype(word)
         self.d = dict.fromkeys(word)
 
+    def test_new_or_init(self):
+        self.assertRaises(TypeError, self.thetype, [], 2)
+
     def test_uniquification(self):
         actual = sorted(self.s)
         expected = sorted(self.d)