One of the things that threw me the first time I did iOS development was the fact network calls were done asynchronously by default. From an implementation side this was nice, I didn’t have to worry about blocking my main thread. But from a testing side… well that was something new.

Since then Apple’s come out with Swift. And with Swift comes the need to learn new ways to do things.  A couple of things I wanted to work out how to do nicely was:  how can I stub out my network layer as I don’t want my test to have to run against a dummy backend, and secondly how can I assert the Optional value I get back is set.

Turns out it wasn’t too tricky. The optional var was set as a result of an async call, so the easiest way to check the value is to first wait till the var has a non nil value.

And stubbing out the network layer was easily achieved by using OHHTTPStubs.

My final test ended up looking like:

func testSubmitsAndProcessesResultFromRemoteService() {
    let service = CoinEntryService()
    let expectedResponse: JSON =  ["amountEnteredSoFar":NSDecimalNumber(double: 2.50), "enoughFundsEntered":false]

    stub(isHost("localhost")) {
        _ in
        return OHHTTPStubsResponse(JSONObject: expectedResponse.rawValue, statusCode: 200, headers: nil)

    var coinEnteredResult: CoinEnteredResult?
    service.coinEntered( {
        result in
        coinEnteredResult = result

    expect(coinEnteredResult?.amountEnteredSoFar).to(equal(NSDecimalNumber(double: 2.5)))