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| 1 | +// Copyright 2025 The Go Authors. All rights reserved. |
| 2 | +// Use of this source code is governed by a BSD-style |
| 3 | +// license that can be found in the LICENSE file. |
| 4 | + |
| 5 | +//go:build goexperiment.synctest |
| 6 | + |
| 7 | +package synctest_test |
| 8 | + |
| 9 | +import ( |
| 10 | + "bufio" |
| 11 | + "bytes" |
| 12 | + "context" |
| 13 | + "fmt" |
| 14 | + "io" |
| 15 | + "net" |
| 16 | + "net/http" |
| 17 | + "strings" |
| 18 | + "testing/synctest" |
| 19 | + "time" |
| 20 | +) |
| 21 | + |
| 22 | +// This example demonstrates testing [http.Transport]'s 100 Continue handling. |
| 23 | +// |
| 24 | +// An HTTP client sending a request can include an "Expect: 100-continue" header |
| 25 | +// to tell the server that the client has additional data to send. |
| 26 | +// The server may then respond with an 100 Continue information response |
| 27 | +// to request the data, or some other status to tell the client the data is not needed. |
| 28 | +// For example, a client uploading a large file might use this feature to confirm |
| 29 | +// that the server is willing to accept the file before sending it. |
| 30 | +// |
| 31 | +// This test confirms that when sending an "Expect: 100-continue" header |
| 32 | +// the HTTP client does not send a request's content before the server requests it, |
| 33 | +// and that it does send the content after receiving a 100 Continue response. |
| 34 | +func Example_httpTransport100Continue() { |
| 35 | + synctest.Run(func() { |
| 36 | + // Create an in-process fake network connection. |
| 37 | + // We cannot use a loopback network connection for this test, |
| 38 | + // because goroutines blocked on network I/O prevent a synctest |
| 39 | + // bubble from becoming idle. |
| 40 | + srvConn, cliConn := net.Pipe() |
| 41 | + defer cliConn.Close() |
| 42 | + defer srvConn.Close() |
| 43 | + |
| 44 | + tr := &http.Transport{ |
| 45 | + // Use the fake network connection created above. |
| 46 | + DialContext: func(ctx context.Context, network, address string) (net.Conn, error) { |
| 47 | + return cliConn, nil |
| 48 | + }, |
| 49 | + // Enable "Expect: 100-continue" handling. |
| 50 | + ExpectContinueTimeout: 5 * time.Second, |
| 51 | + } |
| 52 | + |
| 53 | + // Send a request with the "Expect: 100-continue" header set. |
| 54 | + // Send it in a new goroutine, since it won't complete until the end of the test. |
| 55 | + body := "request body" |
| 56 | + go func() { |
| 57 | + req, err := http.NewRequest("PUT", "http://test.tld/", strings.NewReader(body)) |
| 58 | + if err != nil { |
| 59 | + panic(err) |
| 60 | + } |
| 61 | + req.Header.Set("Expect", "100-continue") |
| 62 | + resp, err := tr.RoundTrip(req) |
| 63 | + if err != nil { |
| 64 | + fmt.Printf("RoundTrip: unexpected error %v\n", err) |
| 65 | + } else { |
| 66 | + resp.Body.Close() |
| 67 | + } |
| 68 | + }() |
| 69 | + |
| 70 | + // Read the request headers sent by the client. |
| 71 | + req, err := http.ReadRequest(bufio.NewReader(srvConn)) |
| 72 | + if err != nil { |
| 73 | + fmt.Printf("ReadRequest: %v\n", err) |
| 74 | + return |
| 75 | + } |
| 76 | + |
| 77 | + // Start a new goroutine copying the body sent by the client into a buffer. |
| 78 | + // Wait for all goroutines in the bubble to block and verify that we haven't |
| 79 | + // read anything from the client yet. |
| 80 | + var gotBody bytes.Buffer |
| 81 | + go io.Copy(&gotBody, req.Body) |
| 82 | + synctest.Wait() |
| 83 | + fmt.Printf("before sending 100 Continue, read body: %q\n", gotBody.String()) |
| 84 | + |
| 85 | + // Write a "100 Continue" response to the client and verify that |
| 86 | + // it sends the request body. |
| 87 | + srvConn.Write([]byte("HTTP/1.1 100 Continue\r\n\r\n")) |
| 88 | + synctest.Wait() |
| 89 | + fmt.Printf("after sending 100 Continue, read body: %q\n", gotBody.String()) |
| 90 | + |
| 91 | + // Finish up by sending the "200 OK" response to conclude the request. |
| 92 | + srvConn.Write([]byte("HTTP/1.1 200 OK\r\n\r\n")) |
| 93 | + |
| 94 | + // We started several goroutines during the test. |
| 95 | + // The synctest.Run call will wait for all of them to exit before returning. |
| 96 | + }) |
| 97 | + |
| 98 | + // Output: |
| 99 | + // before sending 100 Continue, read body: "" |
| 100 | + // after sending 100 Continue, read body: "request body" |
| 101 | +} |
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