Example integration test for API endpoints - tested using Go

api_test.go

// +build integration

package integration

import (
  "bytes"
  "encoding/json"
  "net/http"
  "testing"
)

var endpoint = "http://local.yoursite.com:8080"

func TestCompanyPost(t *testing.T) {
  body := &bytes.Buffer{}
  body.Write([]byte(`{
    "name": "ACME"
  }`))
  req, err := http.NewRequest("POST", endpoint + "/api/companies", body)
  if err != nil {
    t.Fatal(err)
  }
  res, err := http.DefaultClient.Do(req)
  if err != nil {
    t.Fatal(err)
  }
  defer res.Body.Close()
  if res.StatusCode != 201 {
    t.Errorf("got status %d, want %d", res.StatusCode, 201)
  }
  var apiRes map[string]interface{}
  if err := json.NewDecoder(res.Body).Decode(&apiRes); err != nil {
    t.Fatal(err)
  }
  _, ok := apiRes["company"].(map[string]interface{})
  if !ok {
    t.Errorf(`expected response to contain "company" key`, res.StatusCode, 201)
  }
}

With GAE you'd test it with

goapp test ./integration -tags "integration"