How to test UIViewControllers at build time?

Question

I'm a big believer in testing, but not a very good practitioner. I've done pretty well at getting coverage on my model objects and programming them in a TDD style. I'm actually enjoying it so much I'd love to extend this to my controller layer, particularly my UIViewController subclasses.

Unfortunately, many UIKit classes don't function in independent tests. However, I'm unhappy with the restriction of only running my dependent tests on the device. It's really important to me to run all unit tests before every build, and it seems to me like its possible and worthwhile to unit test (as opposed to other types of testing) controller code.

My question is simply this: How do I test UIViewControllers in such a way that the tests run before every build? I am aware of a couple of different solutions to this problem, but don't know a whole lot about the various benefits of each one.

Answer 1

In general if you are stuck with an environmental problem where unconditional testing seems to be made impossible, you can work around it if the benefits are great enough to warrant your jumping through some hoops.

The situation here is a special case of unwanted outside dependencies, which I generally solve in my unit tests by either #ifdefing out tiny bits of dependent code, or by implementing stub classes to fill the expected dependency roles enough that my code can be tested.

So in this specific case, you might create a new source file, linked only in the test bundle, called "UIKitStubClasses.m" … within it you could implement the bare necessities to simulate UIKit dependent classes such as UIViewController, so that your tests link and thoroughly exercise their own logic.

The important thing to remember is this is usually not necessarily all that much work. The tests will let you know what you need to implement in the stub, for example by issuing exceptions about unimplemented methods. You just add what you need to quiet the errors and test your code, and then your stub class is as sufficient for testing as any of the legitimate system framework classes would be.