Correctly using httptest to mock responses

Question

I have something that looks like so:

func (client *MyCustomClient) CheckURL(url string, json_response *MyCustomResponseStruct) bool {
     r, err = http.Get(url)
     if err != nil {
         return false
     }
     defer r.Body.Close()
     .... do stuff with json_response

And in my test, I have the following:

  func TestCheckURL(t *test.T) {
       ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
           w.Header().Set("Content-Type", "text/html; charset=UTF-8")
           fmt.Fprintln(w, `{"status": "success"}`)
       }))
       defer ts.Close()

       json_response := new(MyCustomResponseStruct)
       client := NewMyCustomClient()  // returns instance of MyCustomClient
       done := client.CheckURL("test.com", json_response)

However, it does not appear as if the HTTP test server is working and that it actually goes out to test.com, as evidenced by the log output:

 Get http:/test.com: dial tcp X.Y.Z.A: i/o timeout

My question is how to properly use the httptest package to mock out this request... I read through the docs and this helpful SO Answer but I'm still stuck.

Answer 1

Your client only calls the URL you provided as the first argument to the CheckURL method. Give your client the URL of your test server:

done := client.CheckURL(ts.URL, json_response)