Testing HTTP handlers

The net/http/httptest package also contains ResponseRecorder, which can be used as http.ResponseWriter for HTTP handlers to test a single handler without creating a server.

How to do it...

1. Create ResponseRecorder:

   func TestHandler(t *testing.T) {
     w := httptest.NewRecorder()

2. Call the handler, passing the response recorder instead of http.ResponseWriter:

   data, err := json.Marshal([]time.Time{
     time.Date(2023, 2, 1, 12, 8, 37, 0, time.Local),
     time.Date(2021, 5, 6, 9, 48, 11, 0, time.Local),
     time.Date(2022, 11, 13, 17, 13, 54, 0, time.Local),
     time.Date(2022, 6, 23, 22, 29, 28, 0, time.Local),
     time.Date(2023, 3, 17, 4, 5, 9, 0, time.Local),
   })
   if err != nil {
     t.Error(err)
     return
   }
   req, _ := http.NewRequest("POST", "localhost/sort/asc", bytes.NewReader(data))
   req.Header.Set("Content-Type", "application/json")
   HandleSort(w...