Add tests to DDR experiment

internal/experiment/ddr/ddr.go

@@ -19,6 +19,9 @@ const (
 )
 
 type Config struct {
+	// CustomResolver is the custom resolver to use.
+	// If empty, the system resolver is used.
+	CustomResolver *string
 }
 
 // Measurer performs the measurement.
@@ -70,19 +73,23 @@ func (m *Measurer) Run(
 	ctx, cancel := context.WithTimeout(ctx, timeout)
 	defer cancel()
 
-	systemResolver := getSystemResolverAddress()
-	if systemResolver == "" {
-		return errors.New("could not get system resolver")
+	if m.config.CustomResolver == nil {
+		systemResolver := getSystemResolverAddress()
+		if systemResolver == "" {
+			return errors.New("could not get system resolver")
+		}
+		log.Infof("Using system resolver: %s", systemResolver)
+		tk.Resolver = systemResolver
+	} else {
+		tk.Resolver = *m.config.CustomResolver
 	}
-	log.Infof("Using system resolver: %s", systemResolver)
-	tk.Resolver = systemResolver
 
 	// DDR queries are queries of the SVCB type for the _dns.resolver.arpa. domain.
 
 	netx := &netxlite.Netx{}
 	dialer := netx.NewDialerWithoutResolver(log.Log)
 	transport := netxlite.NewUnwrappedDNSOverUDPTransport(
-		dialer, systemResolver)
+		dialer, tk.Resolver)
 	encoder := &netxlite.DNSEncoderMiekg{}
 	query := encoder.Encode(
 		"_dns.resolver.arpa.", // As specified in RFC 9462

internal/experiment/ddr/ddr_test.go

@@ -1,7 +1,12 @@
 package ddr
 
 import (
+	"context"
 	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/mocks"
+	"github.com/ooni/probe-cli/v3/internal/model"
 )
 
 func TestMeasurerExperimentNameVersion(t *testing.T) {
@@ -13,3 +18,76 @@ func TestMeasurerExperimentNameVersion(t *testing.T) {
 		t.Fatal("unexpected ExperimentVersion")
 	}
 }
+
+func TestMeasurerRun(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
+
+	oneOneOneOneResolver := "1.1.1.1:53"
+
+	measurer := NewExperimentMeasurer(Config{
+		CustomResolver: &oneOneOneOneResolver,
+	})
+	args := &model.ExperimentArgs{
+		Callbacks:   model.NewPrinterCallbacks(log.Log),
+		Measurement: new(model.Measurement),
+		Session: &mocks.Session{
+			MockLogger: func() model.Logger {
+				return log.Log
+			},
+		},
+	}
+	if err := measurer.Run(context.Background(), args); err != nil {
+		t.Fatal(err)
+	}
+	tk := args.Measurement.TestKeys.(*TestKeys)
+	if tk.Failure != nil {
+		t.Fatal("unexpected Failure")
+	}
+
+	if tk.Resolver != oneOneOneOneResolver {
+		t.Fatal("Resolver should be written to TestKeys")
+	}
+
+	// 1.1.1.1 supports DDR
+	if tk.SupportsDDR != true {
+		t.Fatal("unexpected value for Supports DDR")
+	}
+}
+
+// This test fails because the resolver is a domain name and not an IP address.
+func TestMeasurerFailsWithDomainResolver(t *testing.T) {
+	invalidResolver := "invalid-resolver.example:53"
+
+	tk, _ := runExperiment(invalidResolver)
+	if tk.Failure == nil {
+		t.Fatal("expected Failure")
+	}
+}
+
+func TestMeasurerFailsWithNoPort(t *testing.T) {
+	invalidResolver := "1.1.1.1"
+
+	tk, _ := runExperiment(invalidResolver)
+	if tk.Failure == nil {
+		t.Fatal("expected Failure")
+	}
+}
+
+func runExperiment(resolver string) (*TestKeys, error) {
+	measurer := NewExperimentMeasurer(Config{
+		CustomResolver: &resolver,
+	})
+	args := &model.ExperimentArgs{
+		Callbacks:   model.NewPrinterCallbacks(log.Log),
+		Measurement: new(model.Measurement),
+		Session: &mocks.Session{
+			MockLogger: func() model.Logger {
+				return log.Log
+			},
+		},
+	}
+	err := measurer.Run(context.Background(), args)
+	return args.Measurement.TestKeys.(*TestKeys), err
+}