http: fix cookie_test

Was only breaking on some dashboard builds because
not all run the network tests.

R=bradfitzgo, bradfitzwork
CC=golang-dev
https://golang.org/cl/4240086
diff --git a/src/pkg/http/cookie_test.go b/src/pkg/http/cookie_test.go
index 827f232..db09970 100644
--- a/src/pkg/http/cookie_test.go
+++ b/src/pkg/http/cookie_test.go
@@ -6,6 +6,8 @@
 
 import (
 	"bytes"
+	"fmt"
+	"json"
 	"reflect"
 	"testing"
 )
@@ -16,8 +18,12 @@
 	Raw     string
 }{
 	{
-		[]*Cookie{&Cookie{Name: "cookie-1", Value: "v$1", MaxAge: -1}},
-		"Set-Cookie: cookie-1=v$1\r\n",
+		[]*Cookie{
+			&Cookie{Name: "cookie-1", Value: "v$1"},
+			&Cookie{Name: "cookie-2", Value: "two", MaxAge: 3600},
+		},
+		"Set-Cookie: cookie-1=v$1\r\n" +
+			"Set-Cookie: cookie-2=two; Max-Age=3600\r\n",
 	},
 }
 
@@ -38,7 +44,7 @@
 	Raw     string
 }{
 	{
-		[]*Cookie{&Cookie{Name: "cookie-1", Value: "v$1", MaxAge: -1}},
+		[]*Cookie{&Cookie{Name: "cookie-1", Value: "v$1"}},
 		"Cookie: cookie-1=v$1\r\n",
 	},
 }
@@ -61,15 +67,23 @@
 }{
 	{
 		Header{"Set-Cookie": {"Cookie-1=v$1"}},
-		[]*Cookie{&Cookie{Name: "Cookie-1", Value: "v$1", MaxAge: -1, Raw: "Cookie-1=v$1"}},
+		[]*Cookie{&Cookie{Name: "Cookie-1", Value: "v$1", Raw: "Cookie-1=v$1"}},
 	},
 }
 
+func toJSON(v interface{}) string {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return fmt.Sprintf("%#v", v)
+	}
+	return string(b)
+}
+
 func TestReadSetCookies(t *testing.T) {
 	for i, tt := range readSetCookiesTests {
 		c := readSetCookies(tt.Header)
 		if !reflect.DeepEqual(c, tt.Cookies) {
-			t.Errorf("#%d readSetCookies: have\n%#v\nwant\n%#v\n", i, c, tt.Cookies)
+			t.Errorf("#%d readSetCookies: have\n%s\nwant\n%s\n", i, toJSON(c), toJSON(tt.Cookies))
 			continue
 		}
 	}
@@ -81,7 +95,7 @@
 }{
 	{
 		Header{"Cookie": {"Cookie-1=v$1"}},
-		[]*Cookie{&Cookie{Name: "Cookie-1", Value: "v$1", MaxAge: -1, Raw: "Cookie-1=v$1"}},
+		[]*Cookie{&Cookie{Name: "Cookie-1", Value: "v$1"}},
 	},
 }
 
@@ -89,7 +103,7 @@
 	for i, tt := range readCookiesTests {
 		c := readCookies(tt.Header)
 		if !reflect.DeepEqual(c, tt.Cookies) {
-			t.Errorf("#%d readCookies: have\n%#v\nwant\n%#v\n", i, c, tt.Cookies)
+			t.Errorf("#%d readCookies: have\n%s\nwant\n%s\n", i, toJSON(c), toJSON(tt.Cookies))
 			continue
 		}
 	}