Add tests for the C APIs PyCodec_IncrementalEncoder() and
PyCodec_IncrementalDecoder().
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 913aa91..49b534c 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -1,7 +1,7 @@
 from test import test_support
 import unittest
 import codecs
-import sys, StringIO
+import sys, StringIO, _testcapi
 
 class Queue(object):
     """
@@ -1032,9 +1032,11 @@
                     decodedresult += reader.read()
                 self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
-                # check incremental decoder/encoder and iterencode()/iterdecode()
+                # check incremental decoder/encoder (fetched via the Python
+                # and C API) and iterencode()/iterdecode()
                 try:
                     encoder = codecs.getincrementalencoder(encoding)()
+                    cencoder = _testcapi.codec_incrementalencoder(encoding)
                 except LookupError: # no IncrementalEncoder
                     pass
                 else:
@@ -1048,6 +1050,16 @@
                         decodedresult += decoder.decode(c)
                     self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
 
+                    # check C API
+                    encodedresult = ""
+                    for c in s:
+                        encodedresult += cencoder.encode(c)
+                    cdecoder = _testcapi.codec_incrementaldecoder(encoding)
+                    decodedresult = u""
+                    for c in encodedresult:
+                        decodedresult += cdecoder.decode(c)
+                    self.assertEqual(decodedresult, s, "%r != %r (encoding=%r)" % (decodedresult, s, encoding))
+
                     # check iterencode()/iterdecode()
                     result = u"".join(codecs.iterdecode(codecs.iterencode(s, encoding), encoding))
                     self.assertEqual(result, s, "%r != %r (encoding=%r)" % (result, s, encoding))