net/http: speed up tests, use t.Parallel when it's safe

Before: 8.9 seconds for go test -short
 After: 2.8 seconds

There are still 250 tests without t.Parallel, but I got the important
onces using a script:

    $ go test -short -v 2>&1 | go run ~/slowtests.go

Where slowtests.go is https://play.golang.org/p/9mh5Wg1nLN

The remaining 250 (the output lines from slowtests.go) all have a
reported duration of 0ms, except one 50ms test which has to be serial.

Where tests can't be parallel, I left a comment at the top saying why,
so people don't add t.Parallel later and get surprised at failures.

Updates #17751

Change-Id: Icbe32cbe2b996e23c89f1af6339287fa22af5115
Reviewed-on: https://go-review.googlesource.com/32684
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

9 files changed, 127 insertions, 33 deletions

diff --git a/src/net/http/client_test.go b/src/net/http/client_test.go
index 59603def67..7dfd078a41 100644
--- a/src/net/http/client_test.go
+++ b/src/net/http/client_test.go
@@ -197,6 +197,7 @@ func TestPostFormRequestFormat(t *testing.T) {
 }
 
 func TestClientRedirects(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	var ts *httptest.Server
 	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -294,6 +295,7 @@ func TestClientRedirects(t *testing.T) {
 }
 
 func TestClientRedirectContext(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		Redirect(w, r, "/", StatusTemporaryRedirect)
@@ -462,6 +464,7 @@ func testRedirectsByMethod(t *testing.T, method string, table []redirectTest, wa
 }
 
 func TestClientRedirectUseResponse(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	const body = "Hello, world."
 	var ts *httptest.Server
@@ -811,6 +814,7 @@ func TestClientWrites(t *testing.T) {
 }
 
 func TestClientInsecureTransport(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Write([]byte("Hello"))
@@ -1269,6 +1273,7 @@ func testClientTimeout_Headers(t *testing.T, h2 bool) {
 func TestClientRedirectEatsBody_h1(t *testing.T) { testClientRedirectEatsBody(t, h1Mode) }
 func TestClientRedirectEatsBody_h2(t *testing.T) { testClientRedirectEatsBody(t, h2Mode) }
 func testClientRedirectEatsBody(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	saw := make(chan string, 2)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -1580,6 +1585,7 @@ func TestShouldCopyHeaderOnRedirect(t *testing.T) {
 }
 
 func TestClientRedirectTypes(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 
 	tests := [...]struct {
diff --git a/src/net/http/clientserver_test.go b/src/net/http/clientserver_test.go
index d01e7558dc..19dc156003 100644
--- a/src/net/http/clientserver_test.go
+++ b/src/net/http/clientserver_test.go
@@ -170,6 +170,7 @@ func (tt h12Compare) reqFunc() reqFunc {
 }
 
 func (tt h12Compare) run(t *testing.T) {
+	setParallel(t)
 	cst1 := newClientServerTest(t, false, HandlerFunc(tt.Handler), tt.Opts...)
 	defer cst1.close()
 	cst2 := newClientServerTest(t, true, HandlerFunc(tt.Handler), tt.Opts...)
@@ -938,6 +939,7 @@ func testStarRequest(t *testing.T, method string, h2 bool) {
 
 // Issue 13957
 func TestTransportDiscardsUnneededConns(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
 		fmt.Fprintf(w, "Hello, %v", r.RemoteAddr)
@@ -1022,6 +1024,7 @@ func TestTransportGCRequest_Body_h2(t *testing.T)   { testTransportGCRequest(t,
 func TestTransportGCRequest_NoBody_h1(t *testing.T) { testTransportGCRequest(t, h1Mode, false) }
 func TestTransportGCRequest_NoBody_h2(t *testing.T) { testTransportGCRequest(t, h2Mode, false) }
 func testTransportGCRequest(t *testing.T, h2, body bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		ioutil.ReadAll(r.Body)
@@ -1068,6 +1071,7 @@ func TestTransportRejectsInvalidHeaders_h2(t *testing.T) {
 	testTransportRejectsInvalidHeaders(t, h2Mode)
 }
 func testTransportRejectsInvalidHeaders(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		fmt.Fprintf(w, "Handler saw headers: %q", r.Header)
@@ -1200,6 +1204,7 @@ func TestH12_AutoGzipWithDumpResponse(t *testing.T) {
 func TestCloseIdleConnections_h1(t *testing.T) { testCloseIdleConnections(t, h1Mode) }
 func TestCloseIdleConnections_h2(t *testing.T) { testCloseIdleConnections(t, h2Mode) }
 func testCloseIdleConnections(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Header().Set("X-Addr", r.RemoteAddr)
diff --git a/src/net/http/fs_test.go b/src/net/http/fs_test.go
index 3344390cca..55f0debe70 100644
--- a/src/net/http/fs_test.go
+++ b/src/net/http/fs_test.go
@@ -68,6 +68,7 @@ var ServeFileRangeTests = []struct {
 }
 
 func TestServeFile(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		ServeFile(w, r, "testdata/file")
@@ -1064,6 +1065,7 @@ func TestServeContentErrorMessages(t *testing.T) {
 
 // verifies that sendfile is being used on Linux
 func TestLinuxSendfile(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	if runtime.GOOS != "linux" {
 		t.Skip("skipping; linux-only test")
diff --git a/src/net/http/http_test.go b/src/net/http/http_test.go
index aaae67cf29..8f466bb366 100644
--- a/src/net/http/http_test.go
+++ b/src/net/http/http_test.go
@@ -82,6 +82,7 @@ func TestCleanHost(t *testing.T) {
 // This catches accidental dependencies between the HTTP transport and
 // server code.
 func TestCmdGoNoHTTPServer(t *testing.T) {
+	t.Parallel()
 	goBin := testenv.GoToolPath(t)
 	out, err := exec.Command(goBin, "tool", "nm", goBin).CombinedOutput()
 	if err != nil {
diff --git a/src/net/http/npn_test.go b/src/net/http/npn_test.go
index e2e911d3dd..4c1f6b573d 100644
--- a/src/net/http/npn_test.go
+++ b/src/net/http/npn_test.go
@@ -18,6 +18,7 @@ import (
 )
 
 func TestNextProtoUpgrade(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		fmt.Fprintf(w, "path=%s,proto=", r.URL.Path)
diff --git a/src/net/http/response_test.go b/src/net/http/response_test.go
index 342d4f5fc5..660d51791b 100644
--- a/src/net/http/response_test.go
+++ b/src/net/http/response_test.go
@@ -589,6 +589,7 @@ var readResponseCloseInMiddleTests = []struct {
 // reading only part of its contents advances the read to the end of
 // the request, right up until the next request.
 func TestReadResponseCloseInMiddle(t *testing.T) {
+	t.Parallel()
 	for _, test := range readResponseCloseInMiddleTests {
 		fatalf := func(format string, args ...interface{}) {
 			args = append([]interface{}{test.chunked, test.compressed}, args...)
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index fe63c6925f..08b9862e16 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -156,6 +156,7 @@ func (ht handlerTest) rawResponse(req string) string {
 }
 
 func TestConsumingBodyOnNextConn(t *testing.T) {
+	t.Parallel()
 	defer afterTest(t)
 	conn := new(testConn)
 	for i := 0; i < 2; i++ {
@@ -237,6 +238,7 @@ var vtests = []struct {
 }
 
 func TestHostHandlers(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	mux := NewServeMux()
 	for _, h := range handlers {
@@ -353,6 +355,7 @@ var serveMuxTests = []struct {
 }
 
 func TestServeMuxHandler(t *testing.T) {
+	setParallel(t)
 	mux := NewServeMux()
 	for _, e := range serveMuxRegister {
 		mux.Handle(e.pattern, e.h)
@@ -390,6 +393,7 @@ var serveMuxTests2 = []struct {
 // TestServeMuxHandlerRedirects tests that automatic redirects generated by
 // mux.Handler() shouldn't clear the request's query string.
 func TestServeMuxHandlerRedirects(t *testing.T) {
+	setParallel(t)
 	mux := NewServeMux()
 	for _, e := range serveMuxRegister {
 		mux.Handle(e.pattern, e.h)
@@ -432,6 +436,7 @@ func TestServeMuxHandlerRedirects(t *testing.T) {
 
 // Tests for https://golang.org/issue/900
 func TestMuxRedirectLeadingSlashes(t *testing.T) {
+	setParallel(t)
 	paths := []string{"//foo.txt", "///foo.txt", "/../../foo.txt"}
 	for _, path := range paths {
 		req, err := ReadRequest(bufio.NewReader(strings.NewReader("GET " + path + " HTTP/1.1\r\nHost: test\r\n\r\n")))
@@ -536,6 +541,7 @@ func TestServerTimeouts(t *testing.T) {
 // shouldn't cause a handler to block forever on reads (next HTTP
 // request) that will never happen.
 func TestOnlyWriteTimeout(t *testing.T) {
+	setParallel(t)
 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping test; see https://golang.org/issue/7237")
 	}
@@ -598,6 +604,7 @@ func (l trackLastConnListener) Accept() (c net.Conn, err error) {
 
 // TestIdentityResponse verifies that a handler can unset
 func TestIdentityResponse(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	handler := HandlerFunc(func(rw ResponseWriter, req *Request) {
 		rw.Header().Set("Content-Length", "3")
@@ -674,6 +681,7 @@ func TestIdentityResponse(t *testing.T) {
 }
 
 func testTCPConnectionCloses(t *testing.T, req string, h Handler) {
+	setParallel(t)
 	defer afterTest(t)
 	s := httptest.NewServer(h)
 	defer s.Close()
@@ -717,6 +725,7 @@ func testTCPConnectionCloses(t *testing.T, req string, h Handler) {
 }
 
 func testTCPConnectionStaysOpen(t *testing.T, req string, handler Handler) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(handler)
 	defer ts.Close()
@@ -796,6 +805,7 @@ func TestHTTP10KeepAlive304Response(t *testing.T) {
 
 // Issue 15703
 func TestKeepAliveFinalChunkWithEOF(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, false /* h1 */, HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.(Flusher).Flush() // force chunked encoding
@@ -828,6 +838,7 @@ func TestSetsRemoteAddr_h1(t *testing.T) { testSetsRemoteAddr(t, h1Mode) }
 func TestSetsRemoteAddr_h2(t *testing.T) { testSetsRemoteAddr(t, h2Mode) }
 
 func testSetsRemoteAddr(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		fmt.Fprintf(w, "%s", r.RemoteAddr)
@@ -877,6 +888,7 @@ func (c *blockingRemoteAddrConn) RemoteAddr() net.Addr {
 
 // Issue 12943
 func TestServerAllowsBlockingRemoteAddr(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		fmt.Fprintf(w, "RA:%s", r.RemoteAddr)
@@ -948,7 +960,9 @@ func TestServerAllowsBlockingRemoteAddr(t *testing.T) {
 		t.Fatalf("response 1 addr = %q; want %q", g, e)
 	}
 }
+
 func TestIdentityResponseHeaders(t *testing.T) {
+	// Not parallel; changes log output.
 	defer afterTest(t)
 	log.SetOutput(ioutil.Discard) // is noisy otherwise
 	defer log.SetOutput(os.Stderr)
@@ -983,6 +997,7 @@ func TestHeadResponses_h1(t *testing.T) { testHeadResponses(t, h1Mode) }
 func TestHeadResponses_h2(t *testing.T) { testHeadResponses(t, h2Mode) }
 
 func testHeadResponses(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		_, err := w.Write([]byte("<html>"))
@@ -1054,6 +1069,7 @@ func TestTLSHandshakeTimeout(t *testing.T) {
 }
 
 func TestTLSServer(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		if r.TLS != nil {
@@ -1121,6 +1137,7 @@ func TestAutomaticHTTP2_Serve_H2TLSConfig(t *testing.T) {
 }
 
 func testAutomaticHTTP2_Serve(t *testing.T, tlsConf *tls.Config, wantH2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	ln := newLocalListener(t)
 	ln.Close() // immediately (not a defer!)
@@ -1136,6 +1153,7 @@ func testAutomaticHTTP2_Serve(t *testing.T, tlsConf *tls.Config, wantH2 bool) {
 }
 
 func TestAutomaticHTTP2_Serve_WithTLSConfig(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ln := newLocalListener(t)
 	ln.Close() // immediately (not a defer!)
@@ -1177,6 +1195,7 @@ func TestAutomaticHTTP2_ListenAndServe_GetCertificate(t *testing.T) {
 }
 
 func testAutomaticHTTP2_ListenAndServe(t *testing.T, tlsConf *tls.Config) {
+	// Not parallel: uses global test hooks.
 	defer afterTest(t)
 	defer SetTestHookServerServe(nil)
 	var ok bool
@@ -1280,6 +1299,7 @@ var serverExpectTests = []serverExpectTest{
 // correctly.
 // http2 test: TestServer_Response_Automatic100Continue
 func TestServerExpect(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		// Note using r.FormValue("readbody") because for POST
@@ -1373,6 +1393,7 @@ func TestServerExpect(t *testing.T) {
 // Under a ~256KB (maxPostHandlerReadBytes) threshold, the server
 // should consume client request bodies that a handler didn't read.
 func TestServerUnreadRequestBodyLittle(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	conn := new(testConn)
 	body := strings.Repeat("x", 100<<10)
@@ -1413,6 +1434,7 @@ func TestServerUnreadRequestBodyLittle(t *testing.T) {
 // should ignore client request bodies that a handler didn't read
 // and close the connection.
 func TestServerUnreadRequestBodyLarge(t *testing.T) {
+	setParallel(t)
 	if testing.Short() && testenv.Builder() == "" {
 		t.Log("skipping in short mode")
 	}
@@ -1546,6 +1568,7 @@ var handlerBodyCloseTests = [...]handlerBodyCloseTest{
 }
 
 func TestHandlerBodyClose(t *testing.T) {
+	setParallel(t)
 	if testing.Short() && testenv.Builder() == "" {
 		t.Skip("skipping in -short mode")
 	}
@@ -1625,6 +1648,7 @@ var testHandlerBodyConsumers = []testHandlerBodyConsumer{
 }
 
 func TestRequestBodyReadErrorClosesConnection(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	for _, handler := range testHandlerBodyConsumers {
 		conn := new(testConn)
@@ -1655,6 +1679,7 @@ func TestRequestBodyReadErrorClosesConnection(t *testing.T) {
 }
 
 func TestInvalidTrailerClosesConnection(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	for _, handler := range testHandlerBodyConsumers {
 		conn := new(testConn)
@@ -1823,6 +1848,7 @@ func TestRequestBodyTimeoutClosesConnection(t *testing.T) {
 func TestTimeoutHandler_h1(t *testing.T) { testTimeoutHandler(t, h1Mode) }
 func TestTimeoutHandler_h2(t *testing.T) { testTimeoutHandler(t, h2Mode) }
 func testTimeoutHandler(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	sendHi := make(chan bool, 1)
 	writeErrors := make(chan error, 1)
@@ -1876,6 +1902,7 @@ func testTimeoutHandler(t *testing.T, h2 bool) {
 
 // See issues 8209 and 8414.
 func TestTimeoutHandlerRace(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 
 	delayHi := HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -1917,6 +1944,7 @@ func TestTimeoutHandlerRace(t *testing.T) {
 
 // See issues 8209 and 8414.
 func TestTimeoutHandlerRaceHeader(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 
 	delay204 := HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -1952,6 +1980,7 @@ func TestTimeoutHandlerRaceHeader(t *testing.T) {
 
 // Issue 9162
 func TestTimeoutHandlerRaceHeaderTimeout(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	sendHi := make(chan bool, 1)
 	writeErrors := make(chan error, 1)
@@ -2032,6 +2061,7 @@ func TestTimeoutHandlerStartTimerWhenServing(t *testing.T) {
 
 // https://golang.org/issue/15948
 func TestTimeoutHandlerEmptyResponse(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	var handler HandlerFunc = func(w ResponseWriter, _ *Request) {
 		// No response.
@@ -2124,6 +2154,7 @@ func TestZeroLengthPostAndResponse_h2(t *testing.T) {
 }
 
 func testZeroLengthPostAndResponse(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(rw ResponseWriter, r *Request) {
 		all, err := ioutil.ReadAll(r.Body)
@@ -2294,6 +2325,7 @@ func TestServerNoContentType_h1(t *testing.T) { testServerNoHeader(t, h1Mode, "C
 func TestServerNoContentType_h2(t *testing.T) { testServerNoHeader(t, h2Mode, "Content-Type") }
 
 func testServerNoHeader(t *testing.T, h2 bool, header string) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Header()[header] = nil
@@ -2311,6 +2343,7 @@ func testServerNoHeader(t *testing.T, h2 bool, header string) {
 }
 
 func TestStripPrefix(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	h := HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Header().Set("X-Path", r.URL.Path)
@@ -2340,6 +2373,7 @@ func TestStripPrefix(t *testing.T) {
 func TestRequestLimit_h1(t *testing.T) { testRequestLimit(t, h1Mode) }
 func TestRequestLimit_h2(t *testing.T) { testRequestLimit(t, h2Mode) }
 func testRequestLimit(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		t.Fatalf("didn't expect to get request in Handler")
@@ -2386,6 +2420,7 @@ func (cr countReader) Read(p []byte) (n int, err error) {
 func TestRequestBodyLimit_h1(t *testing.T) { testRequestBodyLimit(t, h1Mode) }
 func TestRequestBodyLimit_h2(t *testing.T) { testRequestBodyLimit(t, h2Mode) }
 func testRequestBodyLimit(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	const limit = 1 << 20
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -2481,6 +2516,7 @@ func TestServerBufferedChunking(t *testing.T) {
 // closing the TCP connection, causing the client to get a RST.
 // See https://golang.org/issue/3595
 func TestServerGracefulClose(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		Error(w, "bye", StatusUnauthorized)
@@ -2743,6 +2779,7 @@ func TestHijackAfterCloseNotifier(t *testing.T) {
 }
 
 func TestHijackBeforeRequestBodyRead(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	var requestBody = bytes.Repeat([]byte("a"), 1<<20)
 	bodyOkay := make(chan bool, 1)
@@ -3064,15 +3101,18 @@ func (l *errorListener) Addr() net.Addr {
 }
 
 func TestAcceptMaxFds(t *testing.T) {
-	log.SetOutput(ioutil.Discard) // is noisy otherwise
-	defer log.SetOutput(os.Stderr)
+	setParallel(t)
 
 	ln := &errorListener{[]error{
 		&net.OpError{
 			Op:  "accept",
 			Err: syscall.EMFILE,
 		}}}
-	err := Serve(ln, HandlerFunc(HandlerFunc(func(ResponseWriter, *Request) {})))
+	server := &Server{
+		Handler:  HandlerFunc(HandlerFunc(func(ResponseWriter, *Request) {})),
+		ErrorLog: log.New(ioutil.Discard, "", 0), // noisy otherwise
+	}
+	err := server.Serve(ln)
 	if err != io.EOF {
 		t.Errorf("got error %v, want EOF", err)
 	}
@@ -3197,6 +3237,7 @@ func TestHTTP10ConnectionHeader(t *testing.T) {
 func TestServerReaderFromOrder_h1(t *testing.T) { testServerReaderFromOrder(t, h1Mode) }
 func TestServerReaderFromOrder_h2(t *testing.T) { testServerReaderFromOrder(t, h2Mode) }
 func testServerReaderFromOrder(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	pr, pw := io.Pipe()
 	const size = 3 << 20
@@ -3301,6 +3342,7 @@ func TestTransportAndServerSharedBodyRace_h2(t *testing.T) {
 	testTransportAndServerSharedBodyRace(t, h2Mode)
 }
 func testTransportAndServerSharedBodyRace(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 
 	const bodySize = 1 << 20
@@ -3489,6 +3531,7 @@ func TestAppendTime(t *testing.T) {
 }
 
 func TestServerConnState(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	handler := map[string]func(w ResponseWriter, r *Request){
 		"/": func(w ResponseWriter, r *Request) {
@@ -3536,14 +3579,39 @@ func TestServerConnState(t *testing.T) {
 	}
 	ts.Start()
 
-	mustGet(t, ts.URL+"/")
-	mustGet(t, ts.URL+"/close")
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
 
-	mustGet(t, ts.URL+"/")
-	mustGet(t, ts.URL+"/", "Connection", "close")
+	mustGet := func(url string, headers ...string) {
+		req, err := NewRequest("GET", url, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for len(headers) > 0 {
+			req.Header.Add(headers[0], headers[1])
+			headers = headers[2:]
+		}
+		res, err := c.Do(req)
+		if err != nil {
+			t.Errorf("Error fetching %s: %v", url, err)
+			return
+		}
+		_, err = ioutil.ReadAll(res.Body)
+		defer res.Body.Close()
+		if err != nil {
+			t.Errorf("Error reading %s: %v", url, err)
+		}
+	}
+
+	mustGet(ts.URL + "/")
+	mustGet(ts.URL + "/close")
+
+	mustGet(ts.URL + "/")
+	mustGet(ts.URL+"/", "Connection", "close")
 
-	mustGet(t, ts.URL+"/hijack")
-	mustGet(t, ts.URL+"/hijack-panic")
+	mustGet(ts.URL + "/hijack")
+	mustGet(ts.URL + "/hijack-panic")
 
 	// New->Closed
 	{
@@ -3623,31 +3691,10 @@ func TestServerConnState(t *testing.T) {
 	}
 
 	mu.Lock()
-	t.Errorf("Unexpected events.\nGot log: %s\n   Want: %s\n", logString(stateLog), logString(want))
+	t.Errorf("Unexpected events.\nGot log:\n%s\n   Want:\n%s\n", logString(stateLog), logString(want))
 	mu.Unlock()
 }
 
-func mustGet(t *testing.T, url string, headers ...string) {
-	req, err := NewRequest("GET", url, nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	for len(headers) > 0 {
-		req.Header.Add(headers[0], headers[1])
-		headers = headers[2:]
-	}
-	res, err := DefaultClient.Do(req)
-	if err != nil {
-		t.Errorf("Error fetching %s: %v", url, err)
-		return
-	}
-	_, err = ioutil.ReadAll(res.Body)
-	defer res.Body.Close()
-	if err != nil {
-		t.Errorf("Error reading %s: %v", url, err)
-	}
-}
-
 func TestServerKeepAlivesEnabled(t *testing.T) {
 	defer afterTest(t)
 	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
@@ -3668,6 +3715,7 @@ func TestServerKeepAlivesEnabled(t *testing.T) {
 func TestServerEmptyBodyRace_h1(t *testing.T) { testServerEmptyBodyRace(t, h1Mode) }
 func TestServerEmptyBodyRace_h2(t *testing.T) { testServerEmptyBodyRace(t, h2Mode) }
 func testServerEmptyBodyRace(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	var n int32
 	cst := newClientServerTest(t, h2, HandlerFunc(func(rw ResponseWriter, req *Request) {
@@ -3731,6 +3779,7 @@ func (c *closeWriteTestConn) CloseWrite() error {
 }
 
 func TestCloseWrite(t *testing.T) {
+	setParallel(t)
 	var srv Server
 	var testConn closeWriteTestConn
 	c := ExportServerNewConn(&srv, &testConn)
@@ -3971,6 +4020,7 @@ Host: foo
 // If a Handler finishes and there's an unread request body,
 // verify the server try to do implicit read on it before replying.
 func TestHandlerFinishSkipBigContentLengthRead(t *testing.T) {
+	setParallel(t)
 	conn := &testConn{closec: make(chan bool)}
 	conn.readBuf.Write([]byte(fmt.Sprintf(
 		"POST / HTTP/1.1\r\n" +
@@ -4124,6 +4174,7 @@ func TestServerHandlersCanHandleH2PRI(t *testing.T) {
 // Test that we validate the valid bytes in HTTP/1 headers.
 // Issue 11207.
 func TestServerValidatesHeaders(t *testing.T) {
+	setParallel(t)
 	tests := []struct {
 		header string
 		want   int
@@ -4168,6 +4219,7 @@ func TestServerRequestContextCancel_ServeHTTPDone_h2(t *testing.T) {
 	testServerRequestContextCancel_ServeHTTPDone(t, h2Mode)
 }
 func testServerRequestContextCancel_ServeHTTPDone(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	ctxc := make(chan context.Context, 1)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -4198,6 +4250,7 @@ func testServerRequestContextCancel_ServeHTTPDone(t *testing.T, h2 bool) {
 // is always blocked in a Read call so it notices the EOF from the client.
 // See issues 15927 and 15224.
 func TestServerRequestContextCancel_ConnClose(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	inHandler := make(chan struct{})
 	handlerDone := make(chan struct{})
@@ -4238,6 +4291,7 @@ func TestServerContext_ServerContextKey_h2(t *testing.T) {
 	testServerContext_ServerContextKey(t, h2Mode)
 }
 func testServerContext_ServerContextKey(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		ctx := r.Context()
@@ -4263,6 +4317,7 @@ func testServerContext_ServerContextKey(t *testing.T, h2 bool) {
 
 // https://golang.org/issue/15960
 func TestHandlerSetTransferEncodingChunked(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ht := newHandlerTest(HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Header().Set("Transfer-Encoding", "chunked")
@@ -4277,6 +4332,7 @@ func TestHandlerSetTransferEncodingChunked(t *testing.T) {
 
 // https://golang.org/issue/16063
 func TestHandlerSetTransferEncodingGzip(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ht := newHandlerTest(HandlerFunc(func(w ResponseWriter, r *Request) {
 		w.Header().Set("Transfer-Encoding", "gzip")
@@ -4770,6 +4826,7 @@ func BenchmarkCloseNotifier(b *testing.B) {
 
 // Verify this doesn't race (Issue 16505)
 func TestConcurrentServerServe(t *testing.T) {
+	setParallel(t)
 	for i := 0; i < 100; i++ {
 		ln1 := &oneConnListener{conn: nil}
 		ln2 := &oneConnListener{conn: nil}
@@ -4783,6 +4840,7 @@ func TestServerIdleTimeout(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping in short mode")
 	}
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		io.Copy(ioutil.Discard, r.Body)
@@ -4852,6 +4910,7 @@ func TestServerSetKeepAlivesEnabledClosesConns(t *testing.T) {
 	if runtime.GOOS == "nacl" {
 		t.Skip("skipping on nacl; see golang.org/issue/17695")
 	}
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		io.WriteString(w, r.RemoteAddr)
@@ -4899,6 +4958,7 @@ func TestServerShutdown_h1(t *testing.T) { testServerShutdown(t, h1Mode) }
 func TestServerShutdown_h2(t *testing.T) { testServerShutdown(t, h2Mode) }
 
 func testServerShutdown(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	var doShutdown func() // set later
 	var shutdownRes = make(chan error, 1)
diff --git a/src/net/http/sniff_test.go b/src/net/http/sniff_test.go
index ac404bfa72..38f3f8197e 100644
--- a/src/net/http/sniff_test.go
+++ b/src/net/http/sniff_test.go
@@ -66,6 +66,7 @@ func TestServerContentType_h1(t *testing.T) { testServerContentType(t, h1Mode) }
 func TestServerContentType_h2(t *testing.T) { testServerContentType(t, h2Mode) }
 
 func testServerContentType(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		i, _ := strconv.Atoi(r.FormValue("i"))
@@ -160,6 +161,7 @@ func testContentTypeWithCopy(t *testing.T, h2 bool) {
 func TestSniffWriteSize_h1(t *testing.T) { testSniffWriteSize(t, h1Mode) }
 func TestSniffWriteSize_h2(t *testing.T) { testSniffWriteSize(t, h2Mode) }
 func testSniffWriteSize(t *testing.T, h2 bool) {
+	setParallel(t)
 	defer afterTest(t)
 	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
 		size, _ := strconv.Atoi(r.FormValue("size"))
diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index b3052e146d..f6f21e87ed 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -441,6 +441,7 @@ func TestTransportMaxPerHostIdleConns(t *testing.T) {
 }
 
 func TestTransportRemovesDeadIdleConnections(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		io.WriteString(w, r.RemoteAddr)
@@ -697,6 +698,7 @@ var roundTripTests = []struct {
 
 // Test that the modification made to the Request by the RoundTripper is cleaned up
 func TestRoundTripGzip(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	const responseBody = "test response body"
 	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
@@ -755,6 +757,7 @@ func TestRoundTripGzip(t *testing.T) {
 }
 
 func TestTransportGzip(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	const testString = "The test string aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 	const nRandBytes = 1024 * 1024
@@ -853,6 +856,7 @@ func TestTransportGzip(t *testing.T) {
 // If a request has Expect:100-continue header, the request blocks sending body until the first response.
 // Premature consumption of the request body should not be occurred.
 func TestTransportExpect100Continue(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 
 	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
@@ -1077,7 +1081,7 @@ func waitNumGoroutine(nmax int) int {
 
 // tests that persistent goroutine connections shut down when no longer desired.
 func TestTransportPersistConnLeak(t *testing.T) {
-	setParallel(t)
+	// Not parallel: counts goroutines
 	defer afterTest(t)
 	gotReqCh := make(chan bool)
 	unblockCh := make(chan bool)
@@ -1141,7 +1145,7 @@ func TestTransportPersistConnLeak(t *testing.T) {
 // golang.org/issue/4531: Transport leaks goroutines when
 // request.ContentLength is explicitly short
 func TestTransportPersistConnLeakShortBody(t *testing.T) {
-	setParallel(t)
+	// Not parallel: measures goroutines.
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 	}))
@@ -1237,6 +1241,7 @@ func TestIssue3644(t *testing.T) {
 // Test that a client receives a server's reply, even if the server doesn't read
 // the entire request body.
 func TestIssue3595(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	const deniedMsg = "sorry, denied."
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -1285,6 +1290,7 @@ func TestChunkedNoContent(t *testing.T) {
 }
 
 func TestTransportConcurrency(t *testing.T) {
+	// Not parallel: uses global test hooks.
 	defer afterTest(t)
 	maxProcs, numReqs := 16, 500
 	if testing.Short() {
@@ -1345,6 +1351,7 @@ func TestTransportConcurrency(t *testing.T) {
 }
 
 func TestIssue4191_InfiniteGetTimeout(t *testing.T) {
+	setParallel(t)
 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping test; see https://golang.org/issue/7237")
 	}
@@ -1409,6 +1416,7 @@ func TestIssue4191_InfiniteGetTimeout(t *testing.T) {
 }
 
 func TestIssue4191_InfiniteGetToPutTimeout(t *testing.T) {
+	setParallel(t)
 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping test; see https://golang.org/issue/7237")
 	}
@@ -1930,6 +1938,7 @@ func TestTransportEmptyMethod(t *testing.T) {
 }
 
 func TestTransportSocketLateBinding(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 
 	mux := NewServeMux()
@@ -2194,6 +2203,7 @@ func TestProxyFromEnvironment(t *testing.T) {
 }
 
 func TestIdleConnChannelLeak(t *testing.T) {
+	// Not parallel: uses global test hooks.
 	var mu sync.Mutex
 	var n int
 
@@ -2425,6 +2435,7 @@ func (c byteFromChanReader) Read(p []byte) (n int, err error) {
 // questionable state.
 // golang.org/issue/7569
 func TestTransportNoReuseAfterEarlyResponse(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	var sconn struct {
 		sync.Mutex
@@ -2653,6 +2664,8 @@ func TestTransportClosesBodyOnError(t *testing.T) {
 }
 
 func TestTransportDialTLS(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
 	var mu sync.Mutex // guards following
 	var gotReq, didDial bool
 
@@ -3170,6 +3183,7 @@ func TestTransportReuseConnection_Gzip_ContentLength(t *testing.T) {
 
 // Make sure we re-use underlying TCP connection for gzipped responses too.
 func testTransportReuseConnection_Gzip(t *testing.T, chunked bool) {
+	setParallel(t)
 	defer afterTest(t)
 	addr := make(chan string, 2)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -3205,6 +3219,7 @@ func testTransportReuseConnection_Gzip(t *testing.T, chunked bool) {
 }
 
 func TestTransportResponseHeaderLength(t *testing.T) {
+	setParallel(t)
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		if r.URL.Path == "/long" {
@@ -3643,6 +3658,7 @@ func testTransportIdleConnTimeout(t *testing.T, h2 bool) {
 // know the successful tls.Dial from DialTLS will need to go into the
 // idle pool. Then we give it a of time to explode.
 func TestIdleConnH2Crash(t *testing.T) {
+	setParallel(t)
 	cst := newClientServerTest(t, h2Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
 		// nothing
 	}))