At Zoobe, we have an important component in our backend that is called the “Push Notification Server” or the PNS. The responsibility of the PNS is collecting events through its API, aggregating, generating, localizing, scheduling and finally delivering push notifications to our users. The PNS is written in Go and generates thousands of push notifications everyday. That’s why we have it covered with many unit and functional tests.

The PNS uses Parse’s API for delivering the PNs to the users. One day I thought it may be a good idea to make the deliveryers logs more verbose so I added:

func deliver(){
  // .........
  request, err := getParseRequest(..)
  body, _ := ioutil.ReadAll(request.Body)
  if request != nill {
    _, err := (&http.Client{}).Do(request)
  // .........

You may have noticed the problem by now but back then I didn’t. Also during development I usually have the condition as if false && request != nil to avoid spamming our parse app with useless notifications. The addition was ready and tests were passing so we deployed it. Immediately after deploying it we noticed that all the requests to parse were failing.

The problem with the line I added was that it read the Body Reader before the http client can do, so all the requests were sent to parse with no body. We quickly deployed a fix and everything went back to normal but there were some lessons learned. We didn’t have any thing testing the outgoing requests to a remote server in our test suite. That’s why I developed Smock.

Mocking Remote Servers

Smock is an open source golang package that is used to mock remote servers. It starts a mock server locally, runs a user defined function passing the mock server’s URL to it and collects all the requests that were sent to the server.

Having this package we added many more tests that emulate events and then we expect requests to be sent to the mock server ( as if it is parse ). For example, a sanity check for the like push notification would be written like:

func TestLikeSanityCheck(t *testing.T) {
  reqs := smock.NewMockServer(smock.MockServerConfig{
    MaximumRequestCount: 1,
    GlobalTimeout: 1,
  }).CaptureRequests(func(url string) {
    tmp := config.PARSE_ENDPOINT
    config.PARSE_ENDPOINT = url
    config.PARSE_ENDPOINT = tmp

  assert.Equal(t, 1, len(reqs))
  assert.Equal(t, "{...}", reqs[0].Body)
  assert.Equal(t, "...", reqs[0].Headers.Get("PARSE_APP_KEY"))
  assert.Equal(t, "POST", reqs[0].Method)

The server in the code above expects one request and then it will return. If a request was not received within a one second timeout the server will exit also and the reqs slice will be empty. It may be the case also that the function you call generates a certain amount of requests and then it stops. You can capture the requests sent by this function by what’s called a RequestTimeout. If the RequestTimeout is set, the server has to receive a new request every RequestTimeout seconds or it will exit. The returned status code from the mock server can also be configured.


As I mentioned before, the package is open source and hosted on Github: Your contributions with code, feature requests, issues or ideas are welcome. The code is simple, small and documented so it should be easy to contribute.

Let me know what you think of the package in the comments below. Thanks for reading!

EDIT: The package was previously called RequestBin, but was changed as per the request of @johnsheehan, the CEO of Runscope (The company behind