diff --git a/src/net/lookup_test.go b/src/net/lookup_test.go
index 057e1322b99..430adfd4763 100644
--- a/src/net/lookup_test.go
+++ b/src/net/lookup_test.go
@@ -9,8 +9,10 @@ package net
 
 import (
 	"flag"
+	"fmt"
 	"strings"
 	"testing"
+	"time"
 )
 
 var testExternal = flag.Bool("external", true, "allow use of external networks during long test")
@@ -229,3 +231,66 @@ func TestReverseAddress(t *testing.T) {
 		}
 	}
 }
+
+var testDNSFlood = flag.Bool("dnsflood", false, "whether to test dns query flooding")
+
+func TestLookupIPDeadline(t *testing.T) {
+	if !*testDNSFlood {
+		t.Skip("test disabled; use -dnsflood to enable")
+	}
+
+	const N = 5000
+	const timeout = 3 * time.Second
+	c := make(chan error, 2*N)
+	for i := 0; i < N; i++ {
+		name := fmt.Sprintf("%d.net-test.golang.org", i)
+		go func() {
+			_, err := lookupIPDeadline(name, time.Now().Add(timeout/2))
+			c <- err
+		}()
+		go func() {
+			_, err := lookupIPDeadline(name, time.Now().Add(timeout))
+			c <- err
+		}()
+	}
+	qstats := struct {
+		succeeded, failed         int
+		timeout, temporary, other int
+		unknown                   int
+	}{}
+	deadline := time.After(timeout + time.Second)
+	for i := 0; i < 2*N; i++ {
+		select {
+		case <-deadline:
+			t.Fatal("deadline exceeded")
+		case err := <-c:
+			switch err := err.(type) {
+			case nil:
+				qstats.succeeded++
+			case Error:
+				qstats.failed++
+				if err.Timeout() {
+					qstats.timeout++
+				}
+				if err.Temporary() {
+					qstats.temporary++
+				}
+				if !err.Timeout() && !err.Temporary() {
+					qstats.other++
+				}
+			default:
+				qstats.failed++
+				qstats.unknown++
+			}
+		}
+	}
+
+	// A high volume of DNS queries for sub-domain of golang.org
+	// would be coordinated by authoritative or recursive server,
+	// or stub resolver which implements query-response rate
+	// limitation, so we can expect some query successes and more
+	// failures including timeout, temporary and other here.
+	// As a rule, unknown must not be shown but it might possibly
+	// happen due to issue 4856 for now.
+	t.Logf("%v succeeded, %v failed (%v timeout, %v temporary, %v other, %v unknown)", qstats.succeeded, qstats.failed, qstats.timeout, qstats.temporary, qstats.other, qstats.unknown)
+}
diff --git a/src/net/z_last_test.go b/src/net/z_last_test.go
deleted file mode 100644
index 716c103db26..00000000000
--- a/src/net/z_last_test.go
+++ /dev/null
@@ -1,99 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package net
-
-import (
-	"flag"
-	"fmt"
-	"testing"
-	"time"
-)
-
-var testDNSFlood = flag.Bool("dnsflood", false, "whether to test dns query flooding")
-
-func TestDNSThreadLimit(t *testing.T) {
-	if !*testDNSFlood {
-		t.Skip("test disabled; use -dnsflood to enable")
-	}
-
-	const N = 10000
-	c := make(chan int, N)
-	for i := 0; i < N; i++ {
-		go func(i int) {
-			LookupIP(fmt.Sprintf("%d.net-test.golang.org", i))
-			c <- 1
-		}(i)
-	}
-	// Don't bother waiting for the stragglers; stop at 0.9 N.
-	for i := 0; i < N*9/10; i++ {
-		if i%100 == 0 {
-			//println("TestDNSThreadLimit:", i)
-		}
-		<-c
-	}
-
-	// If we're still here, it worked.
-}
-
-func TestLookupIPDeadline(t *testing.T) {
-	if !*testDNSFlood {
-		t.Skip("test disabled; use -dnsflood to enable")
-	}
-
-	const N = 5000
-	const timeout = 3 * time.Second
-	c := make(chan error, 2*N)
-	for i := 0; i < N; i++ {
-		name := fmt.Sprintf("%d.net-test.golang.org", i)
-		go func() {
-			_, err := lookupIPDeadline(name, time.Now().Add(timeout/2))
-			c <- err
-		}()
-		go func() {
-			_, err := lookupIPDeadline(name, time.Now().Add(timeout))
-			c <- err
-		}()
-	}
-	qstats := struct {
-		succeeded, failed         int
-		timeout, temporary, other int
-		unknown                   int
-	}{}
-	deadline := time.After(timeout + time.Second)
-	for i := 0; i < 2*N; i++ {
-		select {
-		case <-deadline:
-			t.Fatal("deadline exceeded")
-		case err := <-c:
-			switch err := err.(type) {
-			case nil:
-				qstats.succeeded++
-			case Error:
-				qstats.failed++
-				if err.Timeout() {
-					qstats.timeout++
-				}
-				if err.Temporary() {
-					qstats.temporary++
-				}
-				if !err.Timeout() && !err.Temporary() {
-					qstats.other++
-				}
-			default:
-				qstats.failed++
-				qstats.unknown++
-			}
-		}
-	}
-
-	// A high volume of DNS queries for sub-domain of golang.org
-	// would be coordinated by authoritative or recursive server,
-	// or stub resolver which implements query-response rate
-	// limitation, so we can expect some query successes and more
-	// failures including timeout, temporary and other here.
-	// As a rule, unknown must not be shown but it might possibly
-	// happen due to issue 4856 for now.
-	t.Logf("%v succeeded, %v failed (%v timeout, %v temporary, %v other, %v unknown)", qstats.succeeded, qstats.failed, qstats.timeout, qstats.temporary, qstats.other, qstats.unknown)
-}