Add remote test

TODO: hide this behind a -net tag, so it can be disabled.

remote_test.go

@@ -0,0 +1,19 @@
+package dns
+
+import "testing"
+
+const LinodeAddr = "176.58.119.54:53"
+
+func TestClientRemote(t *testing.T) {
+	m := new(Msg)
+	m.SetQuestion("go.dns.miek.nl.", TypeTXT)
+
+	c := new(Client)
+	r, _, err := c.Exchange(m, LinodeAddr)
+	if err != nil {
+		t.Errorf("failed to exchange: %v", err)
+	}
+	if r != nil && r.Rcode != RcodeSuccess {
+		t.Errorf("failed to get an valid answer\n%v", r)
+	}
+}