Boilerplate for testing of code involving DNS lookups, including unholy hacks to redirect net.Lookup* calls.
Trivial mock resolver, for cases where tested code supports custom resolvers:
r := mockdns.Resolver{ Zones: map[string]mockdns.Zone{ "example.org.": { A: []string{"1.2.3.4"}, }, }, } addrs, err := r.LookupHost(context.Background(), "example.org") fmt.Println(addrs, err) // Output: // [1.2.3.4] <nil>Unholy hack for cases where it doesn't:
srv, _ := mockdns.NewServer(map[string]mockdns.Zone{ "example.org.": { A: []string{"1.2.3.4"}, }, }, false) defer srv.Close() srv.PatchNet(net.DefaultResolver) defer mockdns.UnpatchNet(net.DefaultResolver) addrs, err := net.LookupHost("example.org") fmt.Println(addrs, err) // Output: // [1.2.3.4] <nil>Note, if you need to replace net.Dial calls and tested code supports custom net.Dial, patch the resolver object inside it instead of net.DefaultResolver. If tested code supports Dialer-like objects - use Resolver itself, it implements Dial and DialContext methods.