Add PTR serve test

serve_test.go

@@ -130,6 +130,14 @@ func (s *ServeSuite) TestServing(c *C) {
 	r = exchange(c, "one.test.example.com.", dns.TypeA)
 	ip = r.Answer[0].(*dns.A).A
 	c.Check(ip.String(), Equals, "192.168.1.6")
+
+	// PTR
+	r = exchange(c, "2.1.168.192.IN-ADDR.ARPA.", dns.TypePTR)
+	c.Check(r.Answer, HasLen, 1)
+	// NOERROR for PTR request
+	c.Check(r.Rcode, Equals, dns.RcodeSuccess)
+	name := r.Answer[0].(*dns.PTR).Ptr
+	c.Check(name, Equals, "bar.example.com.")
 }
 
 func (s *ServeSuite) TestServingMixedCase(c *C) {