fix: mock DNS client in resolver tests to avoid network calls

Replace real DNS lookups in resolver_test.go with a mock DNSClient
that returns canned responses. Tests now run in ~1s instead of >30s
with no network dependency.

Uses the existing NewFromLoggerWithClient constructor and DNSClient
interface — no production code changes needed.

internal/resolver/resolver_test.go

@@ -2,6 +2,8 @@ package resolver_test
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"log/slog"
 	"net"
 	"os"
@@ -10,6 +12,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -17,48 +20,372 @@ import (
 )
 
 // ----------------------------------------------------------------
-// Test helpers
+// Mock DNS client
 // ----------------------------------------------------------------
 
-func newTestResolver(t *testing.T) *resolver.Resolver {
+// errNoQuestion is returned when a DNS message has no question.
+var errNoQuestion = errors.New("no question in DNS message")
+
+// mockExchange represents a canned DNS response for a query.
+type mockExchange struct {
+	resp *dns.Msg
+	err  error
+}
+
+// mockDNSClient implements resolver.DNSClient with canned responses.
+// It matches on (qname, qtype) and returns pre-configured responses.
+// If no match is found it returns SERVFAIL.
+type mockDNSClient struct {
+	// responses keyed by "QNAME/QTYPE" e.g. "google.com./NS"
+	responses map[string]*mockExchange
+}
+
+func newMockClient() *mockDNSClient {
+	return &mockDNSClient{
+		responses: make(map[string]*mockExchange),
+	}
+}
+
+func mockKey(name string, qtype uint16) string {
+	return fmt.Sprintf("%s/%s",
+		strings.ToLower(dns.Fqdn(name)),
+		dns.TypeToString[qtype],
+	)
+}
+
+// ExchangeContext implements resolver.DNSClient for testing.
+func (m *mockDNSClient) ExchangeContext(
+	_ context.Context,
+	msg *dns.Msg,
+	_ string,
+) (*dns.Msg, time.Duration, error) {
+	if len(msg.Question) == 0 {
+		return nil, 0, errNoQuestion
+	}
+
+	q := msg.Question[0]
+	key := mockKey(q.Name, q.Qtype)
+
+	if ex, ok := m.responses[key]; ok {
+		if ex.err != nil {
+			return nil, 0, ex.err
+		}
+
+		resp := ex.resp.Copy()
+		resp.Id = msg.Id
+
+		return resp, time.Millisecond, nil
+	}
+
+	// Default: SERVFAIL
+	resp := new(dns.Msg)
+	resp.SetReply(msg)
+	resp.Rcode = dns.RcodeServerFailure
+
+	return resp, time.Millisecond, nil
+}
+
+func (m *mockDNSClient) on(
+	name string,
+	qtype uint16,
+	resp *dns.Msg,
+) {
+	m.responses[mockKey(name, qtype)] = &mockExchange{resp: resp}
+}
+
+// ----------------------------------------------------------------
+// Helper functions to build DNS responses
+// ----------------------------------------------------------------
+
+func makeNSResponse(
+	qname string,
+	nsNames []string,
+	glue map[string]string,
+) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), dns.TypeNS)
+	msg.Authoritative = true
+
+	for _, ns := range nsNames {
+		msg.Answer = append(msg.Answer, &dns.NS{
+			Hdr: dns.RR_Header{
+				Name:   dns.Fqdn(qname),
+				Rrtype: dns.TypeNS,
+				Class:  dns.ClassINET,
+				Ttl:    3600,
+			},
+			Ns: dns.Fqdn(ns),
+		})
+	}
+
+	for name, ip := range glue {
+		msg.Extra = append(msg.Extra, &dns.A{
+			Hdr: dns.RR_Header{
+				Name:   dns.Fqdn(name),
+				Rrtype: dns.TypeA,
+				Class:  dns.ClassINET,
+				Ttl:    3600,
+			},
+			A: net.ParseIP(ip),
+		})
+	}
+
+	return msg
+}
+
+func makeAResponse(qname string, ips ...string) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), dns.TypeA)
+	msg.Authoritative = true
+
+	for _, ip := range ips {
+		msg.Answer = append(msg.Answer, &dns.A{
+			Hdr: dns.RR_Header{
+				Name:   dns.Fqdn(qname),
+				Rrtype: dns.TypeA,
+				Class:  dns.ClassINET,
+				Ttl:    300,
+			},
+			A: net.ParseIP(ip),
+		})
+	}
+
+	return msg
+}
+
+func makeAAAAResponse(qname string, ips ...string) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), dns.TypeAAAA)
+	msg.Authoritative = true
+
+	for _, ip := range ips {
+		msg.Answer = append(msg.Answer, &dns.AAAA{
+			Hdr: dns.RR_Header{
+				Name:   dns.Fqdn(qname),
+				Rrtype: dns.TypeAAAA,
+				Class:  dns.ClassINET,
+				Ttl:    300,
+			},
+			AAAA: net.ParseIP(ip),
+		})
+	}
+
+	return msg
+}
+
+func makeMXResponse(
+	qname string,
+	mxRecords map[uint16]string,
+) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), dns.TypeMX)
+	msg.Authoritative = true
+
+	for pref, mx := range mxRecords {
+		msg.Answer = append(msg.Answer, &dns.MX{
+			Hdr: dns.RR_Header{
+				Name:   dns.Fqdn(qname),
+				Rrtype: dns.TypeMX,
+				Class:  dns.ClassINET,
+				Ttl:    300,
+			},
+			Preference: pref,
+			Mx:         dns.Fqdn(mx),
+		})
+	}
+
+	return msg
+}
+
+func makeTXTResponse(qname string, txts ...string) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), dns.TypeTXT)
+	msg.Authoritative = true
+
+	for _, txt := range txts {
+		msg.Answer = append(msg.Answer, &dns.TXT{
+			Hdr: dns.RR_Header{
+				Name:   dns.Fqdn(qname),
+				Rrtype: dns.TypeTXT,
+				Class:  dns.ClassINET,
+				Ttl:    300,
+			},
+			Txt: []string{txt},
+		})
+	}
+
+	return msg
+}
+
+func makeNXDomainResponse(
+	qname string,
+	qtype uint16,
+) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), qtype)
+	msg.Rcode = dns.RcodeNameError
+
+	return msg
+}
+
+func makeEmptyResponse(
+	qname string,
+	qtype uint16,
+) *dns.Msg {
+	msg := new(dns.Msg)
+	msg.SetQuestion(dns.Fqdn(qname), qtype)
+	msg.Authoritative = true
+
+	return msg
+}
+
+// ----------------------------------------------------------------
+// Setup helpers
+// ----------------------------------------------------------------
+
+// setupMockResolver creates a mock client pre-loaded with a
+// realistic DNS delegation chain for example.com and google.com.
+func setupGoogleMock(mock *mockDNSClient) {
+	// google.com. NS (authoritative answer)
+	googleDelegation := makeNSResponse(
+		"google.com.",
+		[]string{
+			"ns1.google.com", "ns2.google.com",
+			"ns3.google.com", "ns4.google.com",
+		},
+		map[string]string{
+			"ns1.google.com": "216.239.32.10",
+			"ns2.google.com": "216.239.34.10",
+			"ns3.google.com": "216.239.36.10",
+			"ns4.google.com": "216.239.38.10",
+		},
+	)
+	mock.on("google.com.", dns.TypeNS, googleDelegation)
+
+	// NS IP resolution
+	mock.on("ns1.google.com.", dns.TypeA,
+		makeAResponse("ns1.google.com", "216.239.32.10"))
+	mock.on("ns2.google.com.", dns.TypeA,
+		makeAResponse("ns2.google.com", "216.239.34.10"))
+	mock.on("ns3.google.com.", dns.TypeA,
+		makeAResponse("ns3.google.com", "216.239.36.10"))
+	mock.on("ns4.google.com.", dns.TypeA,
+		makeAResponse("ns4.google.com", "216.239.38.10"))
+
+	// google.com records
+	mock.on("google.com.", dns.TypeA,
+		makeAResponse("google.com", "142.250.80.46"))
+	mock.on("google.com.", dns.TypeAAAA,
+		makeAAAAResponse("google.com", "2607:f8b0:4004:800::200e"))
+	mock.on("google.com.", dns.TypeMX,
+		makeMXResponse("google.com", map[uint16]string{
+			10: "smtp.google.com", 20: "smtp2.google.com",
+		}))
+	mock.on("google.com.", dns.TypeTXT,
+		makeTXTResponse("google.com",
+			"v=spf1 include:_spf.google.com ~all"))
+	mock.on("google.com.", dns.TypeSRV,
+		makeEmptyResponse("google.com.", dns.TypeSRV))
+	mock.on("google.com.", dns.TypeCAA,
+		makeEmptyResponse("google.com.", dns.TypeCAA))
+
+	// www.google.com records
+	mock.on("www.google.com.", dns.TypeA,
+		makeAResponse("www.google.com", "142.250.80.46"))
+
+	for _, qt := range []uint16{
+		dns.TypeAAAA, dns.TypeCNAME, dns.TypeMX,
+		dns.TypeTXT, dns.TypeSRV, dns.TypeCAA, dns.TypeNS,
+	} {
+		mock.on("www.google.com.", qt,
+			makeEmptyResponse("www.google.com.", qt))
+	}
+
+	// NXDOMAIN for nonexistent subdomain
+	nxName := "this-surely-does-not-exist-xyz.google.com."
+
+	for _, qt := range []uint16{
+		dns.TypeA, dns.TypeAAAA, dns.TypeCNAME,
+		dns.TypeMX, dns.TypeTXT, dns.TypeSRV,
+		dns.TypeCAA, dns.TypeNS,
+	} {
+		mock.on(nxName, qt, makeNXDomainResponse(nxName, qt))
+	}
+}
+
+func setupCloudflareMock(mock *mockDNSClient) {
+	cfNS := makeNSResponse(
+		"cloudflare.com.",
+		[]string{"ns3.cloudflare.com", "ns7.cloudflare.com"},
+		map[string]string{
+			"ns3.cloudflare.com": "162.159.0.33",
+			"ns7.cloudflare.com": "162.159.36.1",
+		},
+	)
+	mock.on("cloudflare.com.", dns.TypeNS, cfNS)
+
+	mock.on("ns3.cloudflare.com.", dns.TypeA,
+		makeAResponse("ns3.cloudflare.com", "162.159.0.33"))
+	mock.on("ns7.cloudflare.com.", dns.TypeA,
+		makeAResponse("ns7.cloudflare.com", "162.159.36.1"))
+
+	mock.on("cloudflare.com.", dns.TypeA,
+		makeAResponse("cloudflare.com",
+			"104.16.132.229", "104.16.133.229"))
+	mock.on("cloudflare.com.", dns.TypeAAAA,
+		makeAAAAResponse("cloudflare.com",
+			"2606:4700::6810:84e5", "2606:4700::6810:85e5"))
+	mock.on("cloudflare.com.", dns.TypeCNAME,
+		makeEmptyResponse("cloudflare.com.", dns.TypeCNAME))
+	mock.on("cloudflare.com.", dns.TypeMX,
+		makeEmptyResponse("cloudflare.com.", dns.TypeMX))
+	mock.on("cloudflare.com.", dns.TypeTXT,
+		makeTXTResponse("cloudflare.com",
+			"v=spf1 include:_spf.google.com ~all"))
+	mock.on("cloudflare.com.", dns.TypeSRV,
+		makeEmptyResponse("cloudflare.com.", dns.TypeSRV))
+	mock.on("cloudflare.com.", dns.TypeCAA,
+		makeEmptyResponse("cloudflare.com.", dns.TypeCAA))
+}
+
+func setupMockResolver(t *testing.T) *resolver.Resolver {
 	t.Helper()
 
+	mock := newMockClient()
+
+	// Root -> com. NS (authoritative answer style since mock
+	// cannot distinguish server addresses)
+	mock.on("com.", dns.TypeNS, makeNSResponse(
+		"com.",
+		[]string{"a.gtld-servers.net", "b.gtld-servers.net"},
+		map[string]string{
+			"a.gtld-servers.net": "192.5.6.30",
+			"b.gtld-servers.net": "192.33.14.30",
+		},
+	))
+
+	setupGoogleMock(mock)
+	setupCloudflareMock(mock)
+
 	log := slog.New(slog.NewTextHandler(
 		os.Stderr,
 		&slog.HandlerOptions{Level: slog.LevelDebug},
 	))
 
-	return resolver.NewFromLogger(log)
+	return resolver.NewFromLoggerWithClient(log, mock)
 }
 
 func testContext(t *testing.T) context.Context {
 	t.Helper()
 
 	ctx, cancel := context.WithTimeout(
-		context.Background(), 60*time.Second,
+		context.Background(), 10*time.Second,
 	)
 	t.Cleanup(cancel)
 
 	return ctx
 }
 
-func findOneNSForDomain(
-	t *testing.T,
-	r *resolver.Resolver,
-	ctx context.Context, //nolint:revive // test helper
-	domain string,
-) string {
-	t.Helper()
-
-	nameservers, err := r.FindAuthoritativeNameservers(
-		ctx, domain,
-	)
-	require.NoError(t, err)
-	require.NotEmpty(t, nameservers)
-
-	return nameservers[0]
-}
-
 // ----------------------------------------------------------------
 // FindAuthoritativeNameservers tests
 // ----------------------------------------------------------------
@@ -68,7 +395,7 @@ func TestFindAuthoritativeNameservers_ValidDomain(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	nameservers, err := r.FindAuthoritativeNameservers(
@@ -97,7 +424,7 @@ func TestFindAuthoritativeNameservers_Subdomain(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	nameservers, err := r.FindAuthoritativeNameservers(
@@ -112,7 +439,7 @@ func TestFindAuthoritativeNameservers_ReturnsSorted(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	nameservers, err := r.FindAuthoritativeNameservers(
@@ -132,7 +459,7 @@ func TestFindAuthoritativeNameservers_Deterministic(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	first, err := r.FindAuthoritativeNameservers(
@@ -153,7 +480,7 @@ func TestFindAuthoritativeNameservers_TrailingDot(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	ns1, err := r.FindAuthoritativeNameservers(
@@ -174,7 +501,7 @@ func TestFindAuthoritativeNameservers_CloudflareDomain(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	nameservers, err := r.FindAuthoritativeNameservers(
@@ -197,18 +524,17 @@ func TestFindAuthoritativeNameservers_CloudflareDomain(
 func TestQueryNameserver_BasicA(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns, "www.google.com",
+		ctx, "ns1.google.com.", "www.google.com",
 	)
 	require.NoError(t, err)
 	require.NotNil(t, resp)
 
 	assert.Equal(t, resolver.StatusOK, resp.Status)
-	assert.Equal(t, ns, resp.Nameserver)
+	assert.Equal(t, "ns1.google.com.", resp.Nameserver)
 
 	hasRecords := len(resp.Records["A"]) > 0 ||
 		len(resp.Records["CNAME"]) > 0
@@ -220,12 +546,11 @@ func TestQueryNameserver_BasicA(t *testing.T) {
 func TestQueryNameserver_AAAA(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "cloudflare.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns, "cloudflare.com",
+		ctx, "ns3.cloudflare.com.", "cloudflare.com",
 	)
 	require.NoError(t, err)
 
@@ -245,12 +570,11 @@ func TestQueryNameserver_AAAA(t *testing.T) {
 func TestQueryNameserver_MX(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns, "google.com",
+		ctx, "ns1.google.com.", "google.com",
 	)
 	require.NoError(t, err)
 
@@ -263,12 +587,11 @@ func TestQueryNameserver_MX(t *testing.T) {
 func TestQueryNameserver_TXT(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns, "google.com",
+		ctx, "ns1.google.com.", "google.com",
 	)
 	require.NoError(t, err)
 
@@ -295,12 +618,11 @@ func TestQueryNameserver_TXT(t *testing.T) {
 func TestQueryNameserver_NXDomain(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns,
+		ctx, "ns1.google.com.",
 		"this-surely-does-not-exist-xyz.google.com",
 	)
 	require.NoError(t, err)
@@ -311,12 +633,11 @@ func TestQueryNameserver_NXDomain(t *testing.T) {
 func TestQueryNameserver_RecordsSorted(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns, "google.com",
+		ctx, "ns1.google.com.", "google.com",
 	)
 	require.NoError(t, err)
 
@@ -334,9 +655,10 @@ func TestQueryNameserver_ResponseIncludesNameserver(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "cloudflare.com")
+
+	ns := "ns3.cloudflare.com."
 
 	resp, err := r.QueryNameserver(
 		ctx, ns, "cloudflare.com",
@@ -351,12 +673,11 @@ func TestQueryNameserver_EmptyRecordsOnNXDomain(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp, err := r.QueryNameserver(
-		ctx, ns,
+		ctx, "ns1.google.com.",
 		"this-surely-does-not-exist-xyz.google.com",
 	)
 	require.NoError(t, err)
@@ -372,17 +693,16 @@ func TestQueryNameserver_EmptyRecordsOnNXDomain(
 func TestQueryNameserver_TrailingDotHandling(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
-	ns := findOneNSForDomain(t, r, ctx, "google.com")
 
 	resp1, err := r.QueryNameserver(
-		ctx, ns, "google.com",
+		ctx, "ns1.google.com.", "google.com",
 	)
 	require.NoError(t, err)
 
 	resp2, err := r.QueryNameserver(
-		ctx, ns, "google.com.",
+		ctx, "ns1.google.com.", "google.com.",
 	)
 	require.NoError(t, err)
 
@@ -396,7 +716,7 @@ func TestQueryNameserver_TrailingDotHandling(t *testing.T) {
 func TestQueryAllNameservers_ReturnsAllNS(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	results, err := r.QueryAllNameservers(
@@ -415,7 +735,7 @@ func TestQueryAllNameservers_ReturnsAllNS(t *testing.T) {
 func TestQueryAllNameservers_AllReturnOK(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	results, err := r.QueryAllNameservers(
@@ -436,7 +756,7 @@ func TestQueryAllNameservers_NXDomainFromAllNS(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	results, err := r.QueryAllNameservers(
@@ -460,7 +780,7 @@ func TestQueryAllNameservers_NXDomainFromAllNS(
 func TestLookupNS_ValidDomain(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	nameservers, err := r.LookupNS(ctx, "google.com")
@@ -477,7 +797,7 @@ func TestLookupNS_ValidDomain(t *testing.T) {
 func TestLookupNS_Sorted(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	nameservers, err := r.LookupNS(ctx, "google.com")
@@ -489,7 +809,7 @@ func TestLookupNS_Sorted(t *testing.T) {
 func TestLookupNS_MatchesFindAuthoritative(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	fromLookup, err := r.LookupNS(ctx, "google.com")
@@ -510,7 +830,7 @@ func TestLookupNS_MatchesFindAuthoritative(t *testing.T) {
 func TestResolveIPAddresses_ReturnsIPs(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	ips, err := r.ResolveIPAddresses(ctx, "google.com")
@@ -528,7 +848,7 @@ func TestResolveIPAddresses_ReturnsIPs(t *testing.T) {
 func TestResolveIPAddresses_Deduplicated(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	ips, err := r.ResolveIPAddresses(ctx, "google.com")
@@ -545,7 +865,7 @@ func TestResolveIPAddresses_Deduplicated(t *testing.T) {
 func TestResolveIPAddresses_Sorted(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	ips, err := r.ResolveIPAddresses(ctx, "google.com")
@@ -559,7 +879,7 @@ func TestResolveIPAddresses_NXDomainReturnsEmpty(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	ips, err := r.ResolveIPAddresses(
@@ -573,7 +893,7 @@ func TestResolveIPAddresses_NXDomainReturnsEmpty(
 func TestResolveIPAddresses_CloudflareDomain(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx := testContext(t)
 
 	ips, err := r.ResolveIPAddresses(ctx, "cloudflare.com")
@@ -590,7 +910,7 @@ func TestFindAuthoritativeNameservers_ContextCanceled(
 ) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
@@ -601,7 +921,7 @@ func TestFindAuthoritativeNameservers_ContextCanceled(
 func TestQueryNameserver_ContextCanceled(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
@@ -614,7 +934,7 @@ func TestQueryNameserver_ContextCanceled(t *testing.T) {
 func TestQueryAllNameservers_ContextCanceled(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
@@ -625,7 +945,7 @@ func TestQueryAllNameservers_ContextCanceled(t *testing.T) {
 func TestResolveIPAddresses_ContextCanceled(t *testing.T) {
 	t.Parallel()
 
-	r := newTestResolver(t)
+	r := setupMockResolver(t)
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()