doudao9896
doudao9896
2018-11-06 11:36

如何在读取响应正文时强加错误

已采纳

I've written http client wrapper in go and I need to test it thoroughly. I'm reading the response body with ioutil.ReadAll within the wrapper. I'm having a bit of trouble figuring out how I can force a read from the response body to fail with the help of httptest.

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
}

I'm assuming I can set up a fake server as such:

package req_test

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")
    }

}

I'm assuming I need to modify the ResposeWriter. Now, is there any way for me to modify the responseWriter and thereby force the ioutil.ReadAll in the wrapper to fail?

I realize that you seem to think it's a duplicate of this post and while you may believe so or it might be, just marking it as a duplicate doesn't really help me. The code provided in the answers in the "duplicate" post makes very little sense to me in this context.

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1条回答

  • doubi4814 doubi4814 3年前

    Check the documentation of Response.Body to see when reading from it might return an error:

    // Body represents the response body.
    //
    // The response body is streamed on demand as the Body field
    // is read. If the network connection fails or the server
    // terminates the response, Body.Read calls return an error.
    //
    // The http Client and Transport guarantee that Body is always
    // non-nil, even on responses without a body or responses with
    // a zero-length body. It is the caller's responsibility to
    // close Body. The default HTTP client's Transport may not
    // reuse HTTP/1.x "keep-alive" TCP connections if the Body is
    // not read to completion and closed.
    //
    // The Body is automatically dechunked if the server replied
    // with a "chunked" Transfer-Encoding.
    Body io.ReadCloser
    

    The easiest way is to generate an invalid HTTP response from the test handler.

    How to do that? There are many ways, a simple one is to "lie" about the content length:

    handler := func(w http.ResponseWriter, r *http.Request) {
        w.Header().Set("Content-Length", "1")
    }
    

    This handler tells it has 1 byte body, but actually it sends none. So at the other end (the client) when attempting to read 1 byte from it, obviously that won't succeed, and will result in the following error:

    Unable to read from body unexpected EOF
    

    See related question if you would need to simulate error reading from a request body (not from a response body): How do I test an error on reading from a request body?

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