func-tests: add answer_count method to Response

tests-extra/tests/dnssec/dnskey_timestamps/data/example.com.zone

-$TTL	1h
-$ORIGIN	example.com.
-
-@		SOA	ns.example.com. admin.example.com. 1 60 60 2419200 3600
-		NS	ns.example.com.
-		A	10.0.0.1
-ns		A	10.0.0.2
-www		A	10.0.0.3

tests-extra/tests/dnssec/dnskey_timestamps/test.py

@@ -6,14 +6,10 @@ Check if DNSKEY lifetime timestamps are proccessed correctly by Knot.
 
 import collections
 import os
-import re
 import shutil
-import sys
-import dns
 
 from dnstest.utils import *
 from dnstest.test import Test
-import dnstest.server
 
 # change timestamps in DNSSEC key file
 def key_settime(filename, **new_values):
@@ -32,21 +28,13 @@ def key_settime(filename, **new_values):
             if value is not None:
                 keyfile.write("%s: %s\n" % (key, value))
 
-# check number of records of given type in DNS answer
-def answer_count(response, rrtype):
-    for rrset in response.answer:
-        if rrset.rdtype == rrtype:
-            return len(rrset)
-    else:
-        return 0
-
 # check zone if keys are present and used for signing
 def check_zone(server, expect_dnskey, expect_rrsig):
     dnskeys = server.dig("example.com", "DNSKEY")
     soa = server.dig("example.com", "SOA", dnssec=True)
 
-    found_dnskeys = answer_count(dnskeys.resp, dns.rdatatype.DNSKEY)
-    found_rrsigs = answer_count(soa.resp, dns.rdatatype.RRSIG)
+    found_dnskeys = dnskeys.answer_count("DNSKEY")
+    found_rrsigs = soa.answer_count("RRSIG")
 
     expect_dnskeys = 2 if expect_dnskey else 1
     expect_rrsigs = 2 if expect_rrsig else 1
@@ -62,7 +50,7 @@ t = Test()
 
 knot = t.server("knot")
 knot.dnssec_enable = True
-zone = t.zone("example.com.", "example.com.zone")
+zone = t.zone("example.com.")
 t.link(zone, knot)
 
 # install keys (one always enabled, one for testing)

tests-extra/tools/dnstest/response.py

@@ -135,3 +135,18 @@ class Response(object):
 
         resp = server.dig(**self.args)
         self.diff(resp, flags, answer, authority, additional)
+
+    def answer_count(self, rtype=None):
+        '''Returns number of records of given type in answer section'''
+
+        if not rtype:
+            rtype = self.rtype
+        elif type(rtype) is str:
+            rtype = dns.rdatatype.from_text(rtype)
+
+        for rrset in self.resp.answer:
+            if rrset.rdtype == rtype:
+                return len(rrset)
+        else:
+            return 0
+