#7475: add (un)transform method to bytes/bytearray and str, add back codecs that can be used with them from Python 2.
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 24ee487..49b50f2 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -207,6 +207,11 @@
         self.assertEqual(b.decode(errors="ignore", encoding="utf8"),
                          "Hello world\n")
 
+    def test_transform(self):
+        b1 = self.type2test(range(256))
+        b2 = b1.transform("base64").untransform("base64")
+        self.assertEqual(b2, b1)
+
     def test_from_int(self):
         b = self.type2test(0)
         self.assertEqual(b, self.type2test())