How to test http calls in Go using httptest

Question

I have the following code:

package main  import (     "encoding/json"     "fmt"     "io/ioutil"     "log"     "net/http"     "time" )  type twitterResult struct {     Results []struct {         Text     string `json:"text"`         Ids      string `json:"id_str"`         Name     string `json:"from_user_name"`         Username string `json:"from_user"`         UserId   string `json:"from_user_id_str"`     } }  var (   twitterUrl = "http://search.twitter.com/search.json?q=%23UCL"   pauseDuration = 5 * time.Second )  func retrieveTweets(c chan<- *twitterResult) {     for {         resp, err := http.Get(twitterUrl)         if err != nil {             log.Fatal(err)         }          defer resp.Body.Close()         body, err := ioutil.ReadAll(resp.Body)         r := new(twitterResult) //or &twitterResult{} which returns *twitterResult         err = json.Unmarshal(body, &r)         if err != nil {             log.Fatal(err)         }         c <- r         time.Sleep(pauseDuration)     }  }  func displayTweets(c chan *twitterResult) {     tweets := <-c     for _, v := range tweets.Results {         fmt.Printf("%v:%v\n", v.Username, v.Text)     }  }  func main() {     c := make(chan *twitterResult)     go retrieveTweets(c)     for {         displayTweets(c)     }  } 

I'd like to write some tests for it, but I'm not sure how to use the httptest package http://golang.org/pkg/net/http/httptest/ would appreciate some pointers

I came up with this (shamelessly copied from the tests for go OAuth https://code.google.com/p/goauth2/source/browse/oauth/oauth_test.go):

var request = struct {     path, query       string // request     contenttype, body string // response }{     path:        "/search.json?",     query:       "q=%23Kenya",     contenttype: "application/json",     body:        twitterResponse, }  var (     twitterResponse = `{ 'results': [{'text':'hello','id_str':'34455w4','from_user_name':'bob','from_user_id_str':'345424'}]}` )  func TestRetrieveTweets(t *testing.T) {     handler := func(w http.ResponseWriter, r *http.Request) {          w.Header().Set("Content-Type", request.contenttype)         io.WriteString(w, request.body)     }      server := httptest.NewServer(http.HandlerFunc(handler))     defer server.Close()      resp, err := http.Get(server.URL)     if err != nil {         t.Fatalf("Get: %v", err)     }     checkBody(t, resp, twitterResponse) }  func checkBody(t *testing.T, r *http.Response, body string) {     b, err := ioutil.ReadAll(r.Body)     if err != nil {         t.Error("reading reponse body: %v, want %q", err, body)     }     if g, w := string(b), body; g != w {         t.Errorf("request body mismatch: got %q, want %q", g, w)     } } 

Answer 1

httptest does two types of tests: response and server

Response test:

func TestHeader3D(t *testing.T) {     resp := httptest.NewRecorder()      uri := "/3D/header/?"     path := "/home/test"     unlno := "997225821"      param := make(url.Values)     param["param1"] = []string{path}     param["param2"] = []string{unlno}      req, err := http.NewRequest("GET", uri+param.Encode(), nil)     if err != nil {             t.Fatal(err)     }      http.DefaultServeMux.ServeHTTP(resp, req)     if p, err := ioutil.ReadAll(resp.Body); err != nil {             t.Fail()     } else {             if strings.Contains(string(p), "Error") {                     t.Errorf("header response shouldn't return error: %s", p)             } else if !strings.Contains(string(p), `expected result`) {                     t.Errorf("header response doen't match:\n%s", p)             }     } } 

Server test (which is what you need to use):

func TestIt(t *testing.T){     ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {         w.Header().Set("Content-Type", "application/json")         fmt.Fprintln(w, `{"fake twitter json string"}`)     }))     defer ts.Close()      twitterUrl = ts.URL     c := make(chan *twitterResult)     go retrieveTweets(c)      tweet := <-c     if tweet != expected1 {         t.Fail()     }     tweet = <-c     if tweet != expected2 {         t.Fail()     } } 

BTW, you don't need to pass in the pointer of r, because it's already a pointer.

err = json.Unmarshal(body, r) 

EDIT: for my recorder test, I could use my http handler like this:

handler(resp, req) 

But my original code is not using the default mux (but from Gorilla/mux), and I have some wrapping around the mux, e.g. insert server logging, and adding request context (Gorilla/context), so I had to start from mux and call ServeHTTP