How to Simulate Response Body Read Errors with httptest?

Simulating Errors on Response Body Read with httptest

When testing HTTP clients with httptest, there may be a need to simulate errors during response body read.

Consider the following wrapper function that consumes response bodies:

<code class="go">package req

func GetContent(url string) ([]byte, error) {
    response, err := httpClient.Get(url)
    // some header validation goes here
    body, err := ioutil.ReadAll(response.Body)
    defer response.Body.Close()

    if err != nil {
        errStr := fmt.Sprintf("Unable to read from body %s", err)
        return nil, errors.New(errStr)
    }

    return body, nil
}</code>

To test this function, a fake server can be set up using httptest:

<code class="go">package req_test

import (
    "net/http"
    "net/http/httptest"
    "testing"
)

func Test_GetContent_RequestBodyReadError(t *testing.T) {

    handler := func(w http.ResponseWriter, r *http.Request) {
        w.WriteHeader(http.StatusOK)
    }

    ts := httptest.NewServer(http.HandlerFunc(handler))
    defer ts.Close()

    _, err := GetContent(ts.URL)

    if err != nil {
        t.Log("Body read failed as expected.")
    } else {
        t.Fatalf("Method did not fail as expected")
    }

}</code>

To force a read error, it's vital to understand the behavior of Response.Body from the documentation:

// Body represents the response body.
//
// ...
// If the network connection fails or the server terminates the response, Body.Read calls return an error.

Therefore, a simple way to simulate an error is to create an invalid HTTP response from the test handler. For instance, lying about the content length can cause an unexpected EOF error on the client side.

An example of such a handler:

<code class="go">handler := func(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Length", "1")
}</code>

The above is the detailed content of How to Simulate Response Body Read Errors with httptest?. For more information, please follow other related articles on the PHP Chinese website!