Table-driven tests for HTTP handlers with httptest

                  package api_test

import (
  "encoding/json"
  "net/http"
  "net/http/httptest"
  "strings"
  "testing"
)

type createThingReq struct {
  Name string `json:"name"`
}

func TestCreateThing(t *testing.T) {
  cases := []struct {
    name   string
    body   string
    status int
  }{
    {name: "missing", body: `{}`, status: http.StatusBadRequest},
    {name: "ok", body: `{"name":"demo"}`, status: http.StatusCreated},
  }

  for _, tc := range cases {
    t.Run(tc.name, func(t *testing.T) {
      r := httptest.NewRequest(http.MethodPost, "/things", strings.NewReader(tc.body))
      w := httptest.NewRecorder()

      handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        var req createThingReq
        if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.Name == "" {
          http.Error(w, "bad request", http.StatusBadRequest)
          return
        }
        w.WriteHeader(http.StatusCreated)
      })

      handler.ServeHTTP(w, r)

      if w.Code != tc.status {
        t.Fatalf("got status %d, want %d", w.Code, tc.status)
      }
    })
  }
}