Initiating ViewDidAppear from UnitTest

Question

Activating ViewDidAppear in UnitTest:

Before getting to my question, I know there is a question very similar to this one (Unit tests don't call viewDidAppear method) but it doesn't seem quite to answer this.

I am wondering how best to activate viewDidAppear() on a viewController to test various things that should occur in that method. I am pretty sure that it is poor practice to call viewDidAppear() directly; so I am wondering how to call it indirectly in a test.

I have followed Natasha's tutorial https://www.natashatherobot.com/ios-testing-view-controllers-swift/ and so have discovered how to activate viewDidLoad() without needing to call it directly. Near the bottom there is discussion of using beginAppearanceTransition(true, animated: true) to call it indirectly, but this does not seem to be having the expected outcome for me.

Any advice? Thanks!

Answer 1

You should call beginAppearanceTransition first for viewWillAppear, and then endAppearanceTransition for viewDidAppear. endAppearanceTransition alone will not execute viewDidAppear:

Swift

 sut.beginAppearanceTransition(true, animated: true)
 sut.endAppearanceTransition()

Objective - C

[self.sut beginAppearanceTransition:YES animated:NO];
[self.sut endAppearanceTransition];

Answer 2

I don't think it's poor practice at all to call viewDidAppear(false) directly for unit testing. I've done so in hundreds of unit tests with no ill effects. After all, viewDidAppear, viewWillAppear and the other lifecycle methods are just that. Methods.

However, I know it's scary to set up view hierarchy for unit tests. With each iOS release, it's uncertain what changes Apple will make to private implementation that may break your view controller tests. But thus far, the only caveat I've seen is sometimes you have to add a controller's view to a window, especially when testing presenting controllers.

I also call loadView() and viewDidLoad() directly. I usually invoke these two methods in the setup portion of a view controller unit test. This prevents me from setting up a complex view controller hierarchy and thus, allows me to test each view controller as a unit.

Calling these methods directly in production code, on the other hand, is poor practice and should be avoided.