Add byte packing/unpacking test

parse_test.go

@@ -1477,3 +1477,32 @@ func TestParseCAA(t *testing.T) {
 		}
 	}
 }
+
+func TestPackCAA(t *testing.T) {
+	m := new(Msg)
+	record := new(CAA)
+	record.Hdr = RR_Header{Name: "example.com.", Rrtype: TypeCAA, Class: ClassINET, Ttl: 0}
+	record.Tag = "issue"
+	record.Value = "symantec.com"
+	record.Flag = 1
+
+	m.Answer = append(m.Answer, record)
+	bytes, err := m.Pack()
+	if err != nil {
+		t.Fatalf("failed to pack msg: %v", err)
+	}
+	if err := m.Unpack(bytes); err != nil {
+		t.Fatalf("failed to unpack msg: %v", err)
+	}
+	if len(m.Answer) != 1 {
+		t.Fatalf("incorrect number of answers unpacked")
+	}
+	rr := m.Answer[0].(*CAA)
+	if rr.Tag != "issue" {
+		t.Fatalf("invalid tag for unpacked answer")
+	} else if rr.Value != "symantec.com" {
+		t.Fatalf("invalid value for unpacked answer")
+	} else if rr.Flag != 1 {
+		t.Fatalf("invalid flag for unpacked answer")
+	}
+}