net/http/httptest: add Client and Certificate methods to Server

Adds a function for easily accessing the x509.Certificate
of a Server, if there is one. Also adds a helper function
for getting a http.Client suitable for use with the server.

This makes the steps required to test a httptest
TLS server simpler.

Fixes #18411

Change-Id: I2e78fe1e54e31bed9c641be2d9a099f698c7bbde
Reviewed-on: https://go-review.googlesource.com/34639
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/go/build/deps_test.go

@@ -411,7 +411,7 @@ var pkgDeps = map[string][]string{
 	"net/http/cgi":       {"L4", "NET", "OS", "crypto/tls", "net/http", "regexp"},
 	"net/http/cookiejar": {"L4", "NET", "net/http"},
 	"net/http/fcgi":      {"L4", "NET", "OS", "net/http", "net/http/cgi"},
-	"net/http/httptest":  {"L4", "NET", "OS", "crypto/tls", "flag", "net/http", "net/http/internal"},
+	"net/http/httptest":  {"L4", "NET", "OS", "crypto/tls", "flag", "net/http", "net/http/internal", "crypto/x509"},
 	"net/http/httputil":  {"L4", "NET", "OS", "context", "net/http", "net/http/internal"},
 	"net/http/pprof":     {"L4", "OS", "html/template", "net/http", "runtime/pprof", "runtime/trace"},
 	"net/rpc":            {"L4", "NET", "encoding/gob", "html/template", "net/http"},

src/net/http/httptest/example_test.go

@@ -54,3 +54,25 @@ func ExampleServer() {
 	fmt.Printf("%s", greeting)
 	// Output: Hello, client
 }
+
+func ExampleNewTLSServer() {
+	ts := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, "Hello, client")
+	}))
+	defer ts.Close()
+
+	client := ts.Client()
+	res, err := client.Get(ts.URL)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	greeting, err := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("%s", greeting)
+	// Output: Hello, client
+}

src/net/http/httptest/server.go

@@ -9,6 +9,7 @@ package httptest
 import (
 	"bytes"
 	"crypto/tls"
+	"crypto/x509"
 	"flag"
 	"fmt"
 	"log"
@@ -35,6 +36,9 @@ type Server struct {
 	// before Start or StartTLS.
 	Config *http.Server
 
+	// certificate is a parsed version of the TLS config certificate, if present.
+	certificate *x509.Certificate
+
 	// wg counts the number of outstanding HTTP requests on this server.
 	// Close blocks until all requests are finished.
 	wg sync.WaitGroup
@@ -42,6 +46,10 @@ type Server struct {
 	mu     sync.Mutex // guards closed and conns
 	closed bool
 	conns  map[net.Conn]http.ConnState // except terminal states
+
+	// client is configured for use with the server.
+	// Its transport is automatically closed when Close is called.
+	client *http.Client
 }
 
 func newLocalListener() net.Listener {
@@ -85,6 +93,7 @@ func NewUnstartedServer(handler http.Handler) *Server {
 	return &Server{
 		Listener: newLocalListener(),
 		Config:   &http.Server{Handler: handler},
+		client:   &http.Client{},
 	}
 }
 
@@ -124,6 +133,17 @@ func (s *Server) StartTLS() {
 	if len(s.TLS.Certificates) == 0 {
 		s.TLS.Certificates = []tls.Certificate{cert}
 	}
+	s.certificate, err = x509.ParseCertificate(s.TLS.Certificates[0].Certificate[0])
+	if err != nil {
+		panic(fmt.Sprintf("httptest: NewTLSServer: %v", err))
+	}
+	certpool := x509.NewCertPool()
+	certpool.AddCert(s.certificate)
+	s.client.Transport = &http.Transport{
+		TLSClientConfig: &tls.Config{
+			RootCAs: certpool,
+		},
+	}
 	s.Listener = tls.NewListener(s.Listener, s.TLS)
 	s.URL = "https://" + s.Listener.Addr().String()
 	s.wrap()
@@ -186,6 +206,11 @@ func (s *Server) Close() {
 		t.CloseIdleConnections()
 	}
 
+	// Also close the client idle connections.
+	if t, ok := s.client.Transport.(closeIdleTransport); ok {
+		t.CloseIdleConnections()
+	}
+
 	s.wg.Wait()
 }
 
@@ -228,6 +253,19 @@ func (s *Server) CloseClientConnections() {
 	}
 }
 
+// Certificate returns the certificate used by the server, or nil if
+// the server doesn't use TLS.
+func (s *Server) Certificate() *x509.Certificate {
+	return s.certificate
+}
+
+// Client returns an HTTP client configured for making requests to the server.
+// It is configured to trust the server's TLS test certificate and will
+// close its idle connections on Server.Close.
+func (s *Server) Client() *http.Client {
+	return s.client
+}
+
 func (s *Server) goServe() {
 	s.wg.Add(1)
 	go func() {

src/net/http/httptest/server_test.go

@@ -22,6 +22,7 @@ func TestServer(t *testing.T) {
 		t.Fatal(err)
 	}
 	got, err := ioutil.ReadAll(res.Body)
+	res.Body.Close()
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -98,3 +99,25 @@ func TestServerCloseClientConnections(t *testing.T) {
 		t.Fatalf("Unexpected response: %#v", res)
 	}
 }
+
+// Tests that the Server.Client method works and returns an http.Client that can hit
+// NewTLSServer without cert warnings.
+func TestServerClient(t *testing.T) {
+	ts := NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("hello"))
+	}))
+	defer ts.Close()
+	client := ts.Client()
+	res, err := client.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "hello" {
+		t.Errorf("got %q, want hello", string(got))
+	}
+}