http2/clientconn_test.go - net - Git at Google

 // Copyright 2024 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.

 // Infrastructure for testing ClientConn.RoundTrip.
 // Put actual tests in transport_test.go.

 package http2

 import (
 	"bytes"
 	"context"
 	"fmt"
 	"io"
 	"net/http"
 	"reflect"
 	"sync/atomic"
 	"testing"
 	"time"

 	"golang.org/x/net/http2/hpack"
 )

 // TestTestClientConn demonstrates usage of testClientConn.
 func TestTestClientConn(t *testing.T) {
 	// newTestClientConn creates a *ClientConn and surrounding test infrastructure.
 	tc := newTestClientConn(t)

 	// tc.greet reads the client's initial SETTINGS and WINDOW_UPDATE frames,
 	// and sends a SETTINGS frame to the client.
 	//
 	// Additional settings may be provided as optional parameters to greet.
 	tc.greet()

 	// Request bodies must either be constant (bytes.Buffer, strings.Reader)
 	// or created with newRequestBody.
 	body := tc.newRequestBody()
 	body.writeBytes(10)         // 10 arbitrary bytes...
 	body.closeWithError(io.EOF) // ...followed by EOF.

 	// tc.roundTrip calls RoundTrip, but does not wait for it to return.
 	// It returns a testRoundTrip.
 	req, _ := http.NewRequest("PUT", "https://dummy.tld/", body)
 	rt := tc.roundTrip(req)

 	// tc has a number of methods to check for expected frames sent.
 	// Here, we look for headers and the request body.
 	tc.wantHeaders(wantHeader{
 		streamID:  rt.streamID(),
 		endStream: false,
 		header: http.Header{
 			":authority": []string{"dummy.tld"},
 			":method":    []string{"PUT"},
 			":path":      []string{"/"},
 		},
 	})
 	// Expect 10 bytes of request body in DATA frames.
 	tc.wantData(wantData{
 		streamID:  rt.streamID(),
 		endStream: true,
 		size:      10,
 		multiple:  true,
 	})

 	// tc.writeHeaders sends a HEADERS frame back to the client.
 	tc.writeHeaders(HeadersFrameParam{
 		StreamID:   rt.streamID(),
 		EndHeaders: true,
 		EndStream:  true,
 		BlockFragment: tc.makeHeaderBlockFragment(
 			":status", "200",
 		),
 	})

 	// Now that we've received headers, RoundTrip has finished.
 	// testRoundTrip has various methods to examine the response,
 	// or to fetch the response and/or error returned by RoundTrip
 	rt.wantStatus(200)
 	rt.wantBody(nil)
 }

 // A testClientConn allows testing ClientConn.RoundTrip against a fake server.
 //
 // A test using testClientConn consists of:
 //   - actions on the client (calling RoundTrip, making data available to Request.Body);
 //   - validation of frames sent by the client to the server; and
 //   - providing frames from the server to the client.
 //
 // testClientConn manages synchronization, so tests can generally be written as
 // a linear sequence of actions and validations without additional synchronization.
 type testClientConn struct {
 	t *testing.T

 	tr    *Transport
 	fr    *Framer
 	cc    *ClientConn
 	group *synctestGroup
 	testConnFramer

 	encbuf bytes.Buffer
 	enc    *hpack.Encoder

 	roundtrips []*testRoundTrip

 	netconn *synctestNetConn
 }

 func newTestClientConnFromClientConn(t *testing.T, cc *ClientConn) *testClientConn {
 	tc := &testClientConn{
 		t:     t,
 		tr:    cc.t,
 		cc:    cc,
 		group: cc.t.transportTestHooks.group.(*synctestGroup),
 	}
 	cli, srv := synctestNetPipe(tc.group)
 	srv.SetReadDeadline(tc.group.Now())
 	srv.autoWait = true
 	tc.netconn = srv
 	tc.enc = hpack.NewEncoder(&tc.encbuf)

 	// all writes and reads are finished.
 	//
 	// cli is the ClientConn's side, srv is the side controlled by the test.
 	cc.tconn = cli
 	tc.fr = NewFramer(srv, srv)
 	tc.testConnFramer = testConnFramer{
 		t:   t,
 		fr:  tc.fr,
 		dec: hpack.NewDecoder(initialHeaderTableSize, nil),
 	}

 	tc.fr.SetMaxReadFrameSize(10 << 20)
 	t.Cleanup(func() {
 		tc.closeWrite()
 	})
 	return tc
 }

 func (tc *testClientConn) readClientPreface() {
 	tc.t.Helper()
 	// Read the client's HTTP/2 preface, sent prior to any HTTP/2 frames.
 	buf := make([]byte, len(clientPreface))
 	if _, err := io.ReadFull(tc.netconn, buf); err != nil {
 		tc.t.Fatalf("reading preface: %v", err)
 	}
 	if !bytes.Equal(buf, clientPreface) {
 		tc.t.Fatalf("client preface: %q, want %q", buf, clientPreface)
 	}
 }

 func newTestClientConn(t *testing.T, opts ...any) *testClientConn {
 	t.Helper()

 	tt := newTestTransport(t, opts...)
 	const singleUse = false
 	_, err := tt.tr.newClientConn(nil, singleUse)
 	if err != nil {
 		t.Fatalf("newClientConn: %v", err)
 	}

 	return tt.getConn()
 }

 // sync waits for the ClientConn under test to reach a stable state,
 // with all goroutines blocked on some input.
 func (tc *testClientConn) sync() {
 	tc.group.Wait()
 }

 // advance advances synthetic time by a duration.
 func (tc *testClientConn) advance(d time.Duration) {
 	tc.group.AdvanceTime(d)
 	tc.sync()
 }

 // hasFrame reports whether a frame is available to be read.
 func (tc *testClientConn) hasFrame() bool {
 	return len(tc.netconn.Peek()) > 0
 }

 // isClosed reports whether the peer has closed the connection.
 func (tc *testClientConn) isClosed() bool {
 	return tc.netconn.IsClosedByPeer()
 }

 // closeWrite causes the net.Conn used by the ClientConn to return a error
 // from Read calls.
 func (tc *testClientConn) closeWrite() {
 	tc.netconn.Close()
 }

 // testRequestBody is a Request.Body for use in tests.
 type testRequestBody struct {
 	tc   *testClientConn
 	gate gate

 	// At most one of buf or bytes can be set at any given time:
 	buf   bytes.Buffer // specific bytes to read from the body
 	bytes int          // body contains this many arbitrary bytes

 	err error // read error (comes after any available bytes)
 }

 func (tc *testClientConn) newRequestBody() *testRequestBody {
 	b := &testRequestBody{
 		tc:   tc,
 		gate: newGate(),
 	}
 	return b
 }

 func (b *testRequestBody) unlock() {
 	b.gate.unlock(b.buf.Len() > 0 || b.bytes > 0 || b.err != nil)
 }

 // Read is called by the ClientConn to read from a request body.
 func (b *testRequestBody) Read(p []byte) (n int, _ error) {
 	if err := b.gate.waitAndLock(context.Background()); err != nil {
 		return 0, err
 	}
 	defer b.unlock()
 	switch {
 	case b.buf.Len() > 0:
 		return b.buf.Read(p)
 	case b.bytes > 0:
 		if len(p) > b.bytes {
 			p = p[:b.bytes]
 		}
 		b.bytes -= len(p)
 		for i := range p {
 			p[i] = 'A'
 		}
 		return len(p), nil
 	default:
 		return 0, b.err
 	}
 }

 // Close is called by the ClientConn when it is done reading from a request body.
 func (b *testRequestBody) Close() error {
 	return nil
 }

 // writeBytes adds n arbitrary bytes to the body.
 func (b *testRequestBody) writeBytes(n int) {
 	defer b.tc.sync()
 	b.gate.lock()
 	defer b.unlock()
 	b.bytes += n
 	b.checkWrite()
 	b.tc.sync()
 }

 // Write adds bytes to the body.
 func (b *testRequestBody) Write(p []byte) (int, error) {
 	defer b.tc.sync()
 	b.gate.lock()
 	defer b.unlock()
 	n, err := b.buf.Write(p)
 	b.checkWrite()
 	return n, err
 }

 func (b *testRequestBody) checkWrite() {
 	if b.bytes > 0 && b.buf.Len() > 0 {
 		b.tc.t.Fatalf("can't interleave Write and writeBytes on request body")
 	}
 	if b.err != nil {
 		b.tc.t.Fatalf("can't write to request body after closeWithError")
 	}
 }

 // closeWithError sets an error which will be returned by Read.
 func (b *testRequestBody) closeWithError(err error) {
 	defer b.tc.sync()
 	b.gate.lock()
 	defer b.unlock()
 	b.err = err
 }

 // roundTrip starts a RoundTrip call.
 //
 // (Note that the RoundTrip won't complete until response headers are received,
 // the request times out, or some other terminal condition is reached.)
 func (tc *testClientConn) roundTrip(req *http.Request) *testRoundTrip {
 	rt := &testRoundTrip{
 		t:     tc.t,
 		donec: make(chan struct{}),
 	}
 	tc.roundtrips = append(tc.roundtrips, rt)
 	go func() {
 		tc.group.Join()
 		defer close(rt.donec)
 		rt.resp, rt.respErr = tc.cc.roundTrip(req, func(cs *clientStream) {
 			rt.id.Store(cs.ID)
 		})
 	}()
 	tc.sync()

 	tc.t.Cleanup(func() {
 		if !rt.done() {
 			return
 		}
 		res, _ := rt.result()
 		if res != nil {
 			res.Body.Close()
 		}
 	})

 	return rt
 }

 func (tc *testClientConn) greet(settings ...Setting) {
 	tc.wantFrameType(FrameSettings)
 	tc.wantFrameType(FrameWindowUpdate)
 	tc.writeSettings(settings...)
 	tc.writeSettingsAck()
 	tc.wantFrameType(FrameSettings) // acknowledgement
 }

 // makeHeaderBlockFragment encodes headers in a form suitable for inclusion
 // in a HEADERS or CONTINUATION frame.
 //
 // It takes a list of alernating names and values.
 func (tc *testClientConn) makeHeaderBlockFragment(s ...string) []byte {
 	if len(s)%2 != 0 {
 		tc.t.Fatalf("uneven list of header name/value pairs")
 	}
 	tc.encbuf.Reset()
 	for i := 0; i < len(s); i += 2 {
 		tc.enc.WriteField(hpack.HeaderField{Name: s[i], Value: s[i+1]})
 	}
 	return tc.encbuf.Bytes()
 }

 // inflowWindow returns the amount of inbound flow control available for a stream,
 // or for the connection if streamID is 0.
 func (tc *testClientConn) inflowWindow(streamID uint32) int32 {
 	tc.cc.mu.Lock()
 	defer tc.cc.mu.Unlock()
 	if streamID == 0 {
 		return tc.cc.inflow.avail + tc.cc.inflow.unsent
 	}
 	cs := tc.cc.streams[streamID]
 	if cs == nil {
 		tc.t.Errorf("no stream with id %v", streamID)
 		return -1
 	}
 	return cs.inflow.avail + cs.inflow.unsent
 }

 // testRoundTrip manages a RoundTrip in progress.
 type testRoundTrip struct {
 	t       *testing.T
 	resp    *http.Response
 	respErr error
 	donec   chan struct{}
 	id      atomic.Uint32
 }

 // streamID returns the HTTP/2 stream ID of the request.
 func (rt *testRoundTrip) streamID() uint32 {
 	id := rt.id.Load()
 	if id == 0 {
 		panic("stream ID unknown")
 	}
 	return id
 }

 // done reports whether RoundTrip has returned.
 func (rt *testRoundTrip) done() bool {
 	select {
 	case <-rt.donec:
 		return true
 	default:
 		return false
 	}
 }

 // result returns the result of the RoundTrip.
 func (rt *testRoundTrip) result() (*http.Response, error) {
 	t := rt.t
 	t.Helper()
 	select {
 	case <-rt.donec:
 	default:
 		t.Fatalf("RoundTrip is not done; want it to be")
 	}
 	return rt.resp, rt.respErr
 }

 // response returns the response of a successful RoundTrip.
 // If the RoundTrip unexpectedly failed, it calls t.Fatal.
 func (rt *testRoundTrip) response() *http.Response {
 	t := rt.t
 	t.Helper()
 	resp, err := rt.result()
 	if err != nil {
 		t.Fatalf("RoundTrip returned unexpected error: %v", rt.respErr)
 	}
 	if resp == nil {
 		t.Fatalf("RoundTrip returned nil *Response and nil error")
 	}
 	return resp
 }

 // err returns the (possibly nil) error result of RoundTrip.
 func (rt *testRoundTrip) err() error {
 	t := rt.t
 	t.Helper()
 	_, err := rt.result()
 	return err
 }

 // wantStatus indicates the expected response StatusCode.
 func (rt *testRoundTrip) wantStatus(want int) {
 	t := rt.t
 	t.Helper()
 	if got := rt.response().StatusCode; got != want {
 		t.Fatalf("got response status %v, want %v", got, want)
 	}
 }

 // body reads the contents of the response body.
 func (rt *testRoundTrip) readBody() ([]byte, error) {
 	t := rt.t
 	t.Helper()
 	return io.ReadAll(rt.response().Body)
 }

 // wantBody indicates the expected response body.
 // (Note that this consumes the body.)
 func (rt *testRoundTrip) wantBody(want []byte) {
 	t := rt.t
 	t.Helper()
 	got, err := rt.readBody()
 	if err != nil {
 		t.Fatalf("unexpected error reading response body: %v", err)
 	}
 	if !bytes.Equal(got, want) {
 		t.Fatalf("unexpected response body:\ngot:  %q\nwant: %q", got, want)
 	}
 }

 // wantHeaders indicates the expected response headers.
 func (rt *testRoundTrip) wantHeaders(want http.Header) {
 	t := rt.t
 	t.Helper()
 	res := rt.response()
 	if diff := diffHeaders(res.Header, want); diff != "" {
 		t.Fatalf("unexpected response headers:\n%v", diff)
 	}
 }

 // wantTrailers indicates the expected response trailers.
 func (rt *testRoundTrip) wantTrailers(want http.Header) {
 	t := rt.t
 	t.Helper()
 	res := rt.response()
 	if diff := diffHeaders(res.Trailer, want); diff != "" {
 		t.Fatalf("unexpected response trailers:\n%v", diff)
 	}
 }

 func diffHeaders(got, want http.Header) string {
 	// nil and 0-length non-nil are equal.
 	if len(got) == 0 && len(want) == 0 {
 		return ""
 	}
 	// We could do a more sophisticated diff here.
 	// DeepEqual is good enough for now.
 	if reflect.DeepEqual(got, want) {
 		return ""
 	}
 	return fmt.Sprintf("got:  %v\nwant: %v", got, want)
 }

 // A testTransport allows testing Transport.RoundTrip against fake servers.
 // Tests that aren't specifically exercising RoundTrip's retry loop or connection pooling
 // should use testClientConn instead.
 type testTransport struct {
 	t     *testing.T
 	tr    *Transport
 	group *synctestGroup

 	ccs []*testClientConn
 }

 func newTestTransport(t *testing.T, opts ...any) *testTransport {
 	tt := &testTransport{
 		t:     t,
 		group: newSynctest(time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)),
 	}
 	tt.group.Join()

 	tr := &Transport{}
 	for _, o := range opts {
 		switch o := o.(type) {
 		case func(*http.Transport):
 			if tr.t1 == nil {
 				tr.t1 = &http.Transport{}
 			}
 			o(tr.t1)
 		case func(*Transport):
 			o(tr)
 		}
 	}
 	tt.tr = tr

 	tr.transportTestHooks = &transportTestHooks{
 		group: tt.group,
 		newclientconn: func(cc *ClientConn) {
 			tc := newTestClientConnFromClientConn(t, cc)
 			tt.ccs = append(tt.ccs, tc)
 		},
 	}

 	t.Cleanup(func() {
 		tt.sync()
 		if len(tt.ccs) > 0 {
 			t.Fatalf("%v test ClientConns created, but not examined by test", len(tt.ccs))
 		}
 		tt.group.Close(t)
 	})

 	return tt
 }

 func (tt *testTransport) sync() {
 	tt.group.Wait()
 }

 func (tt *testTransport) advance(d time.Duration) {
 	tt.group.AdvanceTime(d)
 	tt.sync()
 }

 func (tt *testTransport) hasConn() bool {
 	return len(tt.ccs) > 0
 }

 func (tt *testTransport) getConn() *testClientConn {
 	tt.t.Helper()
 	if len(tt.ccs) == 0 {
 		tt.t.Fatalf("no new ClientConns created; wanted one")
 	}
 	tc := tt.ccs[0]
 	tt.ccs = tt.ccs[1:]
 	tc.sync()
 	tc.readClientPreface()
 	tc.sync()
 	return tc
 }

 func (tt *testTransport) roundTrip(req *http.Request) *testRoundTrip {
 	rt := &testRoundTrip{
 		t:     tt.t,
 		donec: make(chan struct{}),
 	}
 	go func() {
 		tt.group.Join()
 		defer close(rt.donec)
 		rt.resp, rt.respErr = tt.tr.RoundTrip(req)
 	}()
 	tt.sync()

 	tt.t.Cleanup(func() {
 		if !rt.done() {
 			return
 		}
 		res, _ := rt.result()
 		if res != nil {
 			res.Body.Close()
 		}
 	})

 	return rt
 }
	// Copyright 2024 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.

	// Infrastructure for testing ClientConn.RoundTrip.
	// Put actual tests in transport_test.go.

	package http2

	import (
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"sync/atomic"
	"testing"
	"time"

	"golang.org/x/net/http2/hpack"
	)

	// TestTestClientConn demonstrates usage of testClientConn.
	func TestTestClientConn(t *testing.T) {
	// newTestClientConn creates a *ClientConn and surrounding test infrastructure.
	tc := newTestClientConn(t)

	// tc.greet reads the client's initial SETTINGS and WINDOW_UPDATE frames,
	// and sends a SETTINGS frame to the client.
	//
	// Additional settings may be provided as optional parameters to greet.
	tc.greet()

	// Request bodies must either be constant (bytes.Buffer, strings.Reader)
	// or created with newRequestBody.
	body := tc.newRequestBody()
	body.writeBytes(10) // 10 arbitrary bytes...
	body.closeWithError(io.EOF) // ...followed by EOF.

	// tc.roundTrip calls RoundTrip, but does not wait for it to return.
	// It returns a testRoundTrip.
	req, _ := http.NewRequest("PUT", "https://dummy.tld/", body)
	rt := tc.roundTrip(req)

	// tc has a number of methods to check for expected frames sent.
	// Here, we look for headers and the request body.
	tc.wantHeaders(wantHeader{
	streamID: rt.streamID(),
	endStream: false,
	header: http.Header{
	":authority": []string{"dummy.tld"},
	":method": []string{"PUT"},
	":path": []string{"/"},
	},
	})
	// Expect 10 bytes of request body in DATA frames.
	tc.wantData(wantData{
	streamID: rt.streamID(),
	endStream: true,
	size: 10,
	multiple: true,
	})

	// tc.writeHeaders sends a HEADERS frame back to the client.
	tc.writeHeaders(HeadersFrameParam{
	StreamID: rt.streamID(),
	EndHeaders: true,
	EndStream: true,
	BlockFragment: tc.makeHeaderBlockFragment(
	":status", "200",
	),
	})

	// Now that we've received headers, RoundTrip has finished.
	// testRoundTrip has various methods to examine the response,
	// or to fetch the response and/or error returned by RoundTrip
	rt.wantStatus(200)
	rt.wantBody(nil)
	}

	// A testClientConn allows testing ClientConn.RoundTrip against a fake server.
	//
	// A test using testClientConn consists of:
	// - actions on the client (calling RoundTrip, making data available to Request.Body);
	// - validation of frames sent by the client to the server; and
	// - providing frames from the server to the client.
	//
	// testClientConn manages synchronization, so tests can generally be written as
	// a linear sequence of actions and validations without additional synchronization.
	type testClientConn struct {
	t *testing.T

	tr *Transport
	fr *Framer
	cc *ClientConn
	group *synctestGroup
	testConnFramer

	encbuf bytes.Buffer
	enc *hpack.Encoder

	roundtrips []*testRoundTrip

	netconn *synctestNetConn
	}

	func newTestClientConnFromClientConn(t testing.T, cc ClientConn) *testClientConn {
	tc := &testClientConn{
	t: t,
	tr: cc.t,
	cc: cc,
	group: cc.t.transportTestHooks.group.(*synctestGroup),
	}
	cli, srv := synctestNetPipe(tc.group)
	srv.SetReadDeadline(tc.group.Now())
	srv.autoWait = true
	tc.netconn = srv
	tc.enc = hpack.NewEncoder(&tc.encbuf)

	// all writes and reads are finished.
	//
	// cli is the ClientConn's side, srv is the side controlled by the test.
	cc.tconn = cli
	tc.fr = NewFramer(srv, srv)
	tc.testConnFramer = testConnFramer{
	t: t,
	fr: tc.fr,
	dec: hpack.NewDecoder(initialHeaderTableSize, nil),
	}

	tc.fr.SetMaxReadFrameSize(10 << 20)
	t.Cleanup(func() {
	tc.closeWrite()
	})
	return tc
	}

	func (tc *testClientConn) readClientPreface() {
	tc.t.Helper()
	// Read the client's HTTP/2 preface, sent prior to any HTTP/2 frames.
	buf := make([]byte, len(clientPreface))
	if _, err := io.ReadFull(tc.netconn, buf); err != nil {
	tc.t.Fatalf("reading preface: %v", err)
	}
	if !bytes.Equal(buf, clientPreface) {
	tc.t.Fatalf("client preface: %q, want %q", buf, clientPreface)
	}
	}

	func newTestClientConn(t testing.T, opts ...any) testClientConn {
	t.Helper()

	tt := newTestTransport(t, opts...)
	const singleUse = false
	_, err := tt.tr.newClientConn(nil, singleUse)
	if err != nil {
	t.Fatalf("newClientConn: %v", err)
	}

	return tt.getConn()
	}

	// sync waits for the ClientConn under test to reach a stable state,
	// with all goroutines blocked on some input.
	func (tc *testClientConn) sync() {
	tc.group.Wait()
	}

	// advance advances synthetic time by a duration.
	func (tc *testClientConn) advance(d time.Duration) {
	tc.group.AdvanceTime(d)
	tc.sync()
	}

	// hasFrame reports whether a frame is available to be read.
	func (tc *testClientConn) hasFrame() bool {
	return len(tc.netconn.Peek()) > 0
	}

	// isClosed reports whether the peer has closed the connection.
	func (tc *testClientConn) isClosed() bool {
	return tc.netconn.IsClosedByPeer()
	}

	// closeWrite causes the net.Conn used by the ClientConn to return a error
	// from Read calls.
	func (tc *testClientConn) closeWrite() {
	tc.netconn.Close()
	}

	// testRequestBody is a Request.Body for use in tests.
	type testRequestBody struct {
	tc *testClientConn
	gate gate

	// At most one of buf or bytes can be set at any given time:
	buf bytes.Buffer // specific bytes to read from the body
	bytes int // body contains this many arbitrary bytes

	err error // read error (comes after any available bytes)
	}

	func (tc testClientConn) newRequestBody() testRequestBody {
	b := &testRequestBody{
	tc: tc,
	gate: newGate(),
	}
	return b
	}

	func (b *testRequestBody) unlock() {
	b.gate.unlock(b.buf.Len() > 0 \|\| b.bytes > 0 \|\| b.err != nil)
	}

	// Read is called by the ClientConn to read from a request body.
	func (b *testRequestBody) Read(p []byte) (n int, _ error) {
	if err := b.gate.waitAndLock(context.Background()); err != nil {
	return 0, err
	}
	defer b.unlock()
	switch {
	case b.buf.Len() > 0:
	return b.buf.Read(p)
	case b.bytes > 0:
	if len(p) > b.bytes {
	p = p[:b.bytes]
	}
	b.bytes -= len(p)
	for i := range p {
	p[i] = 'A'
	}
	return len(p), nil
	default:
	return 0, b.err
	}
	}

	// Close is called by the ClientConn when it is done reading from a request body.
	func (b *testRequestBody) Close() error {
	return nil
	}

	// writeBytes adds n arbitrary bytes to the body.
	func (b *testRequestBody) writeBytes(n int) {
	defer b.tc.sync()
	b.gate.lock()
	defer b.unlock()
	b.bytes += n
	b.checkWrite()
	b.tc.sync()
	}

	// Write adds bytes to the body.
	func (b *testRequestBody) Write(p []byte) (int, error) {
	defer b.tc.sync()
	b.gate.lock()
	defer b.unlock()
	n, err := b.buf.Write(p)
	b.checkWrite()
	return n, err
	}

	func (b *testRequestBody) checkWrite() {
	if b.bytes > 0 && b.buf.Len() > 0 {
	b.tc.t.Fatalf("can't interleave Write and writeBytes on request body")
	}
	if b.err != nil {
	b.tc.t.Fatalf("can't write to request body after closeWithError")
	}
	}

	// closeWithError sets an error which will be returned by Read.
	func (b *testRequestBody) closeWithError(err error) {
	defer b.tc.sync()
	b.gate.lock()
	defer b.unlock()
	b.err = err
	}

	// roundTrip starts a RoundTrip call.
	//
	// (Note that the RoundTrip won't complete until response headers are received,
	// the request times out, or some other terminal condition is reached.)
	func (tc testClientConn) roundTrip(req http.Request) *testRoundTrip {
	rt := &testRoundTrip{
	t: tc.t,
	donec: make(chan struct{}),
	}
	tc.roundtrips = append(tc.roundtrips, rt)
	go func() {
	tc.group.Join()
	defer close(rt.donec)
	rt.resp, rt.respErr = tc.cc.roundTrip(req, func(cs *clientStream) {
	rt.id.Store(cs.ID)
	})
	}()
	tc.sync()

	tc.t.Cleanup(func() {
	if !rt.done() {
	return
	}
	res, _ := rt.result()
	if res != nil {
	res.Body.Close()
	}
	})

	return rt
	}

	func (tc *testClientConn) greet(settings ...Setting) {
	tc.wantFrameType(FrameSettings)
	tc.wantFrameType(FrameWindowUpdate)
	tc.writeSettings(settings...)
	tc.writeSettingsAck()
	tc.wantFrameType(FrameSettings) // acknowledgement
	}

	// makeHeaderBlockFragment encodes headers in a form suitable for inclusion
	// in a HEADERS or CONTINUATION frame.
	//
	// It takes a list of alernating names and values.
	func (tc *testClientConn) makeHeaderBlockFragment(s ...string) []byte {
	if len(s)%2 != 0 {
	tc.t.Fatalf("uneven list of header name/value pairs")
	}
	tc.encbuf.Reset()
	for i := 0; i < len(s); i += 2 {
	tc.enc.WriteField(hpack.HeaderField{Name: s[i], Value: s[i+1]})
	}
	return tc.encbuf.Bytes()
	}

	// inflowWindow returns the amount of inbound flow control available for a stream,
	// or for the connection if streamID is 0.
	func (tc *testClientConn) inflowWindow(streamID uint32) int32 {
	tc.cc.mu.Lock()
	defer tc.cc.mu.Unlock()
	if streamID == 0 {
	return tc.cc.inflow.avail + tc.cc.inflow.unsent
	}
	cs := tc.cc.streams[streamID]
	if cs == nil {
	tc.t.Errorf("no stream with id %v", streamID)
	return -1
	}
	return cs.inflow.avail + cs.inflow.unsent
	}

	// testRoundTrip manages a RoundTrip in progress.
	type testRoundTrip struct {
	t *testing.T
	resp *http.Response
	respErr error
	donec chan struct{}
	id atomic.Uint32
	}

	// streamID returns the HTTP/2 stream ID of the request.
	func (rt *testRoundTrip) streamID() uint32 {
	id := rt.id.Load()
	if id == 0 {
	panic("stream ID unknown")
	}
	return id
	}

	// done reports whether RoundTrip has returned.
	func (rt *testRoundTrip) done() bool {
	select {
	case <-rt.donec:
	return true
	default:
	return false
	}
	}

	// result returns the result of the RoundTrip.
	func (rt testRoundTrip) result() (http.Response, error) {
	t := rt.t
	t.Helper()
	select {
	case <-rt.donec:
	default:
	t.Fatalf("RoundTrip is not done; want it to be")
	}
	return rt.resp, rt.respErr
	}

	// response returns the response of a successful RoundTrip.
	// If the RoundTrip unexpectedly failed, it calls t.Fatal.
	func (rt testRoundTrip) response() http.Response {
	t := rt.t
	t.Helper()
	resp, err := rt.result()
	if err != nil {
	t.Fatalf("RoundTrip returned unexpected error: %v", rt.respErr)
	}
	if resp == nil {
	t.Fatalf("RoundTrip returned nil *Response and nil error")
	}
	return resp
	}

	// err returns the (possibly nil) error result of RoundTrip.
	func (rt *testRoundTrip) err() error {
	t := rt.t
	t.Helper()
	_, err := rt.result()
	return err
	}

	// wantStatus indicates the expected response StatusCode.
	func (rt *testRoundTrip) wantStatus(want int) {
	t := rt.t
	t.Helper()
	if got := rt.response().StatusCode; got != want {
	t.Fatalf("got response status %v, want %v", got, want)
	}
	}

	// body reads the contents of the response body.
	func (rt *testRoundTrip) readBody() ([]byte, error) {
	t := rt.t
	t.Helper()
	return io.ReadAll(rt.response().Body)
	}

	// wantBody indicates the expected response body.
	// (Note that this consumes the body.)
	func (rt *testRoundTrip) wantBody(want []byte) {
	t := rt.t
	t.Helper()
	got, err := rt.readBody()
	if err != nil {
	t.Fatalf("unexpected error reading response body: %v", err)
	}
	if !bytes.Equal(got, want) {
	t.Fatalf("unexpected response body:\ngot: %q\nwant: %q", got, want)
	}
	}

	// wantHeaders indicates the expected response headers.
	func (rt *testRoundTrip) wantHeaders(want http.Header) {
	t := rt.t
	t.Helper()
	res := rt.response()
	if diff := diffHeaders(res.Header, want); diff != "" {
	t.Fatalf("unexpected response headers:\n%v", diff)
	}
	}

	// wantTrailers indicates the expected response trailers.
	func (rt *testRoundTrip) wantTrailers(want http.Header) {
	t := rt.t
	t.Helper()
	res := rt.response()
	if diff := diffHeaders(res.Trailer, want); diff != "" {
	t.Fatalf("unexpected response trailers:\n%v", diff)
	}
	}

	func diffHeaders(got, want http.Header) string {
	// nil and 0-length non-nil are equal.
	if len(got) == 0 && len(want) == 0 {
	return ""
	}
	// We could do a more sophisticated diff here.
	// DeepEqual is good enough for now.
	if reflect.DeepEqual(got, want) {
	return ""
	}
	return fmt.Sprintf("got: %v\nwant: %v", got, want)
	}

	// A testTransport allows testing Transport.RoundTrip against fake servers.
	// Tests that aren't specifically exercising RoundTrip's retry loop or connection pooling
	// should use testClientConn instead.
	type testTransport struct {
	t *testing.T
	tr *Transport
	group *synctestGroup

	ccs []*testClientConn
	}

	func newTestTransport(t testing.T, opts ...any) testTransport {
	tt := &testTransport{
	t: t,
	group: newSynctest(time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)),
	}
	tt.group.Join()

	tr := &Transport{}
	for _, o := range opts {
	switch o := o.(type) {
	case func(*http.Transport):
	if tr.t1 == nil {
	tr.t1 = &http.Transport{}
	}
	o(tr.t1)
	case func(*Transport):
	o(tr)
	}
	}
	tt.tr = tr

	tr.transportTestHooks = &transportTestHooks{
	group: tt.group,
	newclientconn: func(cc *ClientConn) {
	tc := newTestClientConnFromClientConn(t, cc)
	tt.ccs = append(tt.ccs, tc)
	},
	}

	t.Cleanup(func() {
	tt.sync()
	if len(tt.ccs) > 0 {
	t.Fatalf("%v test ClientConns created, but not examined by test", len(tt.ccs))
	}
	tt.group.Close(t)
	})

	return tt
	}

	func (tt *testTransport) sync() {
	tt.group.Wait()
	}

	func (tt *testTransport) advance(d time.Duration) {
	tt.group.AdvanceTime(d)
	tt.sync()
	}

	func (tt *testTransport) hasConn() bool {
	return len(tt.ccs) > 0
	}

	func (tt testTransport) getConn() testClientConn {
	tt.t.Helper()
	if len(tt.ccs) == 0 {
	tt.t.Fatalf("no new ClientConns created; wanted one")
	}
	tc := tt.ccs[0]
	tt.ccs = tt.ccs[1:]
	tc.sync()
	tc.readClientPreface()
	tc.sync()
	return tc
	}

	func (tt testTransport) roundTrip(req http.Request) *testRoundTrip {
	rt := &testRoundTrip{
	t: tt.t,
	donec: make(chan struct{}),
	}
	go func() {
	tt.group.Join()
	defer close(rt.donec)
	rt.resp, rt.respErr = tt.tr.RoundTrip(req)
	}()
	tt.sync()

	tt.t.Cleanup(func() {
	if !rt.done() {
	return
	}
	res, _ := rt.result()
	if res != nil {
	res.Body.Close()
	}
	})

	return rt
	}