View Controller TDD

Question

I am trying to add some unit tests to my project to test view controllers. However I seem to be having problems with seemingly simple things. I have created a sample project which I will refer to. https://github.com/pangers/ViewControllerTesting

The sample contains a UINavigationController as the initial view controller. The root view controller of the UINavigationController is FirstViewController. There is a button on FirstViewController that segues to SecondViewController. In SecondViewController there is an empty textfield.

The two tests I am trying to add are:
1) Check button title in FirstViewController is "Next Screen".
2) Check textfield in SecondViewController is empty, "".

I have heard reports of adding your swift files to both the main target and the test target is not good practice. But rather it is better to make whatever you want to access in your tests public and import the main target into the tests. So that is what I have done. (I have also set the "Defines Module" for the main target to YES as that is what I have read in a few articles aswell).

In FirstViewControllerTests I have instantiated the first view controller with the following:

var viewController: FirstViewController!

override func setUp() {
    let storyboard = UIStoryboard(name: "Main", bundle: NSBundle(forClass: self.dynamicType))
    let navigationController = storyboard.instantiateInitialViewController() as UINavigationController
    viewController = navigationController.topViewController as FirstViewController
    viewController.viewDidLoad()
}

And I have added the test:

func testCheckButtonHasTextNextScreen() {
    XCTAssertEqual(viewController.button.currentTitle!, "Next Screen", "Button should say Next Screen")
}

Similarly, for SecondViewControllerTest, I have set it up using:

var secondViewController:SecondViewController!

override func setUp() {
    let storyboard = UIStoryboard(name: "Main", bundle: NSBundle(forClass: self.dynamicType))
    let navigationController = storyboard.instantiateInitialViewController() as UINavigationController
    let firstviewController = navigationController.topViewController as FirstViewController
    firstviewController.performSegueWithIdentifier("FirstToSecond", sender: nil)
    secondViewController = navigationController.topViewController as SecondViewController
    secondViewController.viewDidLoad()
}

And the test:

func testTextFieldIsBlank() {
    XCTAssertEqual(secondViewController.textField.text, "", "Nothing in textfield")
}

They both fail and I am not too sure as to why. My suspicion is that the way I am instantiating the view controllers is not correct. Is the best way to instantiate the view controllers is to use the storyboard (just like it would if it were to run in real life)? Or is it acceptable to be instantiated via:

var viewController = FirstViewController()

What are you guys' experience with TDD and view controllers in swift?

I am using Swift with XCode 6.1.1.

Thanks in advance.

Solved

Ok after considering the answers from modocache and Mike Taverne, I've found my solution and I've learnt a few things which I will write down below.

1) I made anything class/method/variable that I want to test public. I do not need to add the swift files to the test target.

2) I only needed to set "Defines Module" for the "Main" target (as opposed to the "Test" target or the entire project)

3) When instantiating the storyboard, the bundle should be set to nil rather than NSBundle(forClass: self.dynamicType), otherwise tests will fail.

4) As modocache stated, it is good to give your view controller's a StoryboardID and instantiate them like so:

viewController = storyboard.instantiateViewControllerWithIdentifier("FirstViewController") as FirstViewController

However, instantiating the view controller like this ONLY instantiates the view controller alone, and not any navigation controllers that it may be embedded in. That means, attempting to do

XCTAssertFalse(viewController.navigationController!.navigationBarHidden, "Bar should show by default")

will result in a nil exception. I confirmed this with

XCTAssertNil(viewController.navigationController?, "navigation controller doesn't exist")

which resulted in a successful test.

Since I wanted to check the state of the navigation bar in FirstViewController, you must instantiate the view controller like so:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let navigationController = storyboard.instantiateInitialViewController() as UINavigationController
viewController = navigationController.topViewController as FirstViewController

Now performing the test

XCTAssertFalse(viewController.navigationController!.navigationBarHidden, "nav bar should be showing by default")

results in a successful test.

5) let _ = viewController.view does indeed trigger viewDidLoad() which was confirmed by a test

6) let _ = viewController.view does not trigger viewWillAppear(), and I presume anything afterwards aswell. viewController.viewWillAppear(false/true) needs to be called manually to trigger it (Confirmed by a test).

Hopefully this will be of help to people. I will push the updated project to GitHub (link above) if anyone would like to play around with it.

Update #2

After all the above, I still could not figure out how to transition from the first view controller to the second view controller (so that I may test navigation bar properties in SecondViewControllerTests.swift). I tried

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let nc = storyboard.instantiateInitialViewController() as UINavigationController
let firstVC = nc.topViewController as FirstViewController
firstVC.performSegueWithIdentifier("FirstToSecond", sender: nil)
secondVC = nc.topViewController as SecondViewController

which caused an error.

I also tried

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let nc = storyboard.instantiateInitialViewController() as UINavigationController
let firstVC = nc.topViewController as FirstViewController
firstVC.toSecondVCButton.sendActionsForControlEvents(UIControlEvents.TouchUpInside)
secondVC = nc.topViewController as SecondViewController

which did not work.

I eventually tried

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let nc = storyboard.instantiateInitialViewController() as UINavigationController
vc = storyboard.instantiateViewControllerWithIdentifier("Second") as SecondViewController
nc.pushViewController(vc, animated: false)
let _ = vc.view
vc.viewWillAppear(false)

which worked perfectly with my tests (allowed me to access navigation bar properties)!

Answer 1

I agree with @MikeTaverne's answer: I prefer accessing -[UIViewController view] in order to trigger -[UIViewController viewDidLoad], rather than calling it directly. See if the test failures for FirstViewController go away once you use this instead:

viewController = navigationController.topViewController as FirstViewController
let _  = viewController.view

I'd also recommend giving both view controllers identifiers in your storyboard. This will allow you to instantiate them directly, without accessing them via UINavigationController:

var secondViewController: SecondViewController!

override func setUp() {
    let storyboard = UIStoryboard(name: "Main", bundle: NSBundle(forClass: self.dynamicType))
    secondViewController = storyboard.instantiateViewControllerWithIdentifier("SecondViewController")
        as SecondViewController
    let _ = secondViewController.view
}

Check out my talk on testing UIViewController at Brooklyn Swift for details: https://vimeo.com/115671189#t=37m50s (my presentation begins around the 37'50" mark).

Answer 2

I've begun unit testing view controllers recently, and it poses some unique challenges.

One challenge is getting the view to load. Looking at your set up for FirstViewController, you are trying to do this with viewController.viewDidLoad().

My suggestion is to replace that line with this:

let dummy = viewController.view

Accessing the .view property will force the view to load. This will trigger the .viewDidLoad in your ViewController, so don't call that method explicitly in your test.

This approach is considered hacky by some people, but it is simple and effective. (See Clean way to force view to load subviews early)

As an aside, I am finding the best way to test view controllers is to move as much code out of the view controllers as possible into other classes that are more easily tested.

If your view controller is defined in a storyboard, then you need to instantiate it that way for your outlets to be set up properly. Trying to initialize it like an ordinary class won't work.