Most apps in the App Store perform networking in one way or the other. Apple provides a great class for network requests—
NSURLSession. Its requests are asynchronous. This means that the response is delivered on a background thread. If that wasn't the case, the UI would freeze while the app waits for a response from the server.
The main topic of this chapter is how to test an asynchronous API. There are two ways to write tests for asynchronous API calls. Firstly, using asynchronous tests provided by the
XCTest framework. Secondly, using stubs as we did in the previous chapter.
Both methods have their advantages. Asynchronous tests let us test whether the web server is implemented as described in the documentation. ...