How to mock second try of http call? - go

Question

As part of my first project I am creating a tiny library to send an SMS to any user. I have added the logic of waiting and retrying if it doesn't receive a positive status on first go. It's a basic HTTP call to am SMS sending service. My algorithm looks like this (comments would explain the flow of the code):
for {
//send request
resp, err := HTTPClient.Do(req)
checkOK, checkSuccessUrl, checkErr := CheckSuccessStatus(resp, err)
//if successful don't continue
if !checkOK and checkErr != nil {
err = checkErr
return resp, SUCCESS, int8(RetryMax-remain+1), err
}
remain := remain - 1
if remain == 0 {
break
}
//calculate wait time
wait := Backoff(RetryWaitMin, RetryWaitMax, RetryMax-remain, resp)
//wait for time calculated in backoff above
time.Sleep(wait)
//check the status of last call, if unsuccessful then continue the loop
if checkSuccessUrl != "" {
req, err := GetNotificationStatusCheckRequest(checkSuccessUrl)
resp, err := HTTPClient.Do(req)
checkOK, _, checkErr = CheckSuccessStatusBeforeRetry(resp, err)
if !checkOK {
if checkErr != nil {
err = checkErr
}
return resp,SUCCESS, int8(RetryMax-remain), err
}
}
}
Now I want to test this logic using any HTTP mock framework available. The best I've got is https://github.com/jarcoal/httpmock
But this one does not provide functionality to mock the response of first and second URL separately. Hence I cannot test the success in second or third retry. I can either test success in first go or failure altogether.
Is there a package out there which suits my needs of testing this particular feature? If no, How can I achieve this using current tools?

Answer 1

This can easily be achieved using the test server that comes in the standard library's httptest package. With a slight modification to the example contained within it you can set up functions for each of the responses you want up front by doing this:
package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"net/http/httptest"
)
func main() {
responseCounter := 0
responses := []func(w http.ResponseWriter, r *http.Request){
func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, "First response")
},
func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, "Second response")
},
}
ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
responses[responseCounter](w, r)
responseCounter++
}))
defer ts.Close()
printBody(ts.URL)
printBody(ts.URL)
}
func printBody(url string) {
res, err := http.Get(url)
if err != nil {
log.Fatal(err)
}
resBody, err := ioutil.ReadAll(res.Body)
res.Body.Close()
if err != nil {
log.Fatal(err)
}
fmt.Printf("%s", resBody)
}
Which outputs:
First response
Second response
Executable code here:
https://play.golang.org/p/YcPe5hOSxlZ

Answer 2

Not sure you still need an answer, but github.com/jarcoal/httpmock provides a way to do this using ResponderFromMultipleResponses.