diff --git a/attacker/resolver_test.go b/attacker/resolver_test.go
new file mode 100644
index 0000000..34a1099
--- /dev/null
+++ b/attacker/resolver_test.go
@@ -0,0 +1,92 @@
+package attacker
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+const (
+	testDomain       = "test.notadomain"
+	DNSServerAddress = "127.0.0.1"
+	message          = "Test Server"
+)
+
+func TestNewResolver(t *testing.T) {
+	done := make(chan struct{}) // for ensuring ds.PacketConn is not nil
+
+	// prepare custom DNS server
+	dns.HandleFunc(".", handleRequest)
+	ds := dns.Server{
+		Addr:              DNSServerAddress + ":0",
+		Net:               "udp",
+		ReadTimeout:       time.Millisecond * time.Duration(2000),
+		WriteTimeout:      time.Millisecond * time.Duration(2000),
+		NotifyStartedFunc: func() { close(done) },
+	}
+
+	go func() {
+		if err := ds.ListenAndServe(); err != nil {
+			t.Logf("got error during dns ListenAndServe: %s", err)
+		}
+	}()
+	defer func() {
+		_ = ds.Shutdown()
+	}()
+
+	<-done
+
+	net.DefaultResolver = NewResolver([]string{ds.PacketConn.LocalAddr().String()})
+
+	// test server for name resolution
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, message)
+	}))
+	defer ts.Close()
+
+	tsURL, _ := url.Parse(ts.URL)
+	_, port, _ := net.SplitHostPort(tsURL.Host)
+	tsURL.Host = net.JoinHostPort(testDomain, port)
+
+	resp, err := http.Get(tsURL.String())
+	if err != nil {
+		t.Fatalf("failed resolver round trip: %v", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatalf("failed to read respose body: %v", err)
+	}
+
+	if strings.TrimSpace(string(body)) != message {
+		t.Errorf("reponse body mismatch, expected: '%s', but got '%s'", message, body)
+	}
+}
+
+func handleRequest(w dns.ResponseWriter, r *dns.Msg) {
+	m := new(dns.Msg)
+	m.SetReply(r)
+
+	m.Answer = []dns.RR{
+		&dns.A{
+			Hdr: dns.RR_Header{
+				Name:   r.Question[0].Name,
+				Rrtype: dns.TypeA,
+				Class:  dns.ClassINET,
+				Ttl:    1,
+			},
+			A: net.ParseIP(DNSServerAddress),
+		},
+	}
+
+	w.WriteMsg(m)
+}
diff --git a/go.mod b/go.mod
index df55a86..68c68bc 100644
--- a/go.mod
+++ b/go.mod
@@ -7,6 +7,7 @@ require (
 	github.com/k0kubun/colorstring v0.0.0-20150214042306-9440f1994b88 // indirect
 	github.com/k0kubun/pp v3.0.1+incompatible
 	github.com/mattn/go-colorable v0.1.7 // indirect
+	github.com/miekg/dns v1.1.17
 	github.com/mum4k/termdash v0.12.2
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.6.1
diff --git a/go.sum b/go.sum
index 069f46c..d7e8e57 100644
--- a/go.sum
+++ b/go.sum
@@ -60,6 +60,7 @@ github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Ky
 github.com/mattn/go-runewidth v0.0.4/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
 github.com/mattn/go-runewidth v0.0.9 h1:Lm995f3rfxdpd6TSmuVCHVb/QhupuXlYr8sCI/QdE+0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
+github.com/miekg/dns v1.1.17 h1:BhJxdA7bH51vKFZSY8Sn9pR7++LREvg0eYFzHA452ew=
 github.com/miekg/dns v1.1.17/go.mod h1:WgzbA6oji13JREwiNsRDNfl7jYdPnmz+VEuLrA+/48M=
 github.com/mum4k/termdash v0.12.2 h1:S2frz71OrXUKIVVZ3snYBEzyYlUNRTu0ElV6d5Pf6gI=
 github.com/mum4k/termdash v0.12.2/go.mod h1:haerPCSO0U8pehROAecmuOHDF+2UXw2KaCTxdWooDFE=
@@ -84,6 +85,7 @@ go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
 go.uber.org/goleak v1.1.10 h1:z+mqJhf6ss6BSfSM671tgKyZBFPTTJM+HLxnhPC3wu0=
 go.uber.org/goleak v1.1.10/go.mod h1:8a7PlsEVH3e/a/GLqe5IIrQx6GzcnRmZEufDUTk4A7A=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472 h1:Gv7RPwsi3eZ2Fgewe3CBsuOebPwO27PoXzRpJPsvSSM=
 golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de h1:5hukYrvBGR8/eNkX5mdUezrA6JiaEZDtJb9Ei+1LlBs=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=