Programming iOS 6, 3rd Edition

Unit Testing

Another way of verifying the correctness of your code is through unit tests. A unit test is basically a suite of methods that call methods of your app’s code and use asserts to describe what should happen. Typically, unit tests are constructed so as to confirm not only that the app behaves as expected under normal conditions, but also that incorrect or extreme inputs are handled properly. There’s even a school of thought that suggests you should write unit tests before writing the real code.

The easiest way to attach unit tests to your app is at the time you create the project: in the second dialog, check Include Unit Tests. Xcode endows your project with a secondary target, which is a Unit Testing Bundle consisting of the test code and linked to the SenTestingKit framework. The unit testing target has a dependency on the normal target; thus, if you build the normal target, you build your app normally, but if you build the unit testing target, you build your app along with the unit testing bundle.

To run unit tests against your app, you choose Product → Test. The project’s scheme specifies that this means to build the unit testing target, and lists the test methods that are to be run; to specify particular test methods, edit the scheme.

You can subsequently add another Unit Testing Bundle target to your project if you like. When you do, an additional scheme is created. So, to run the tests in an added unit testing target, you’d change the scheme selection in the Scheme ...