[trac914] added some utilities for further testing:

 - allow pydnspp.TSIGContext to act as a base class so that we can define
   a mock class for easier testing
 - define MockTSIGContext (for now) as a transparent wrapper, and use this
   class in existing tests to confirm it doesn't change the behavior.

src/bin/xfrin/tests/xfrin_test.py

@@ -15,6 +15,7 @@
 
 import unittest
 import socket
+from isc.testutils.tsigctx_mock import MockTSIGContext
 from xfrin import *
 
 #
@@ -225,7 +226,7 @@ class TestXfrinConnection(unittest.TestCase):
         self.assertEqual(self.conn.query_data, b'\x00\x1d\x105\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x07example\x03com\x00\x00\xfc\x00\x01')
 
         # soa request with tsig
-        self.conn._tsig_ctx = TSIGContext(TSIG_KEY)
+        self.conn._tsig_ctx = MockTSIGContext(TSIG_KEY)
         self.conn._send_query(RRType.SOA())
         tsig_soa_data = strip_mutable_tsig_data(self.conn.query_data)
         self.assertEqual(tsig_soa_data, b'\x00n\x105\x00\x00\x00\x01\x00\x00\x00\x00\x00\x01\x07example\x03com\x00\x00\x06\x00\x01\x07example\x03com\x00\x00\xfa\x00\xff\x00\x00\x00\x00\x00:\x08hmac-md5\x07sig-alg\x03reg\x03int\x00\x01,\x00\x10\x105\x00\x00\x00\x00')
@@ -240,7 +241,7 @@ class TestXfrinConnection(unittest.TestCase):
         self.assertRaises(XfrinTestException, self._handle_xfrin_response)
 
     def test_response_with_tsig(self):
-        self.conn._tsig_ctx = TSIGContext(TSIG_KEY)
+        self.conn._tsig_ctx = MockTSIGContext(TSIG_KEY)
         # server tsig check fail, return with RCODE 9 (NOTAUTH)
         self.conn._send_query(RRType.SOA())
         self.conn.reply_data = self.conn.create_response_data(rcode=Rcode.NOTAUTH())

src/lib/dns/python/tsig_python.cc

@@ -270,7 +270,14 @@ PyTypeObject tsigcontext_type = {
     NULL,                               // tp_getattro
     NULL,                               // tp_setattro
     NULL,                               // tp_as_buffer
-    Py_TPFLAGS_DEFAULT,                 // tp_flags
+
+    // We allow the python version of TSIGContext to act as a base class.
+    // From pure design point of view, this is wrong because it's not intended
+    // to be inherited.  However, cryptographic operations are generally
+    // difficult to test, so it would be very advantageous if we can define
+    // a mock context class.
+    Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE, // tp_flags
+
     "The TSIGContext class objects is...(COMPLETE THIS)",
     NULL,                               // tp_traverse
     NULL,                               // tp_clear

src/lib/python/isc/testutils/tsigctx_mock.py

@@ -0,0 +1,30 @@
+# Copyright (C) 2011  Internet Systems Consortium.
+#
+# Permission to use, copy, modify, and distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SYSTEMS CONSORTIUM
+# DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
+# INTERNET SYSTEMS CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
+# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
+# FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
+# WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+from pydnspp import *
+
+class MockTSIGContext(TSIGContext):
+    """Tthis is a mock of TSIGContext class for testing"""
+
+    def __init__(self, tsig_key):
+        super().__init__(tsig_key)
+
+    def sign(self, qid, data):
+        """Transparently delegate the processing to the super class.
+        It doesn't matter much anyway because normal applications that would
+        be implemented in Python normally won't call TSIGContext.sign()
+        directly.
+        """
+        return super().sign(qid, data)