Can't cast custom UIViewController from UIStoryboard in XCTest

ahalls picture ahalls · Aug 17, 2014 · Viewed 14.5k times · Source

In Swift, Xcode6-Beta5, I'm trying to unit test my "ViewController", not a very creative name.

From looking at other responses, I'm thinking I don't have my "Tests" target configured properly.

Failing test code:

  func testItShouldLoadFromStoryboard() {

    var storyBoard: UIStoryboard?
    var anyVC: AnyObject?
    var viewController: ViewController?
    var uiViewController: UIViewController?

    storyBoard = UIStoryboard(name:"Main", bundle: nil)
    XCTAssert(storyBoard != nil, "Test Not Configured Properly")

    anyVC = storyBoard?.instantiateInitialViewController()
    viewController = anyVC  as? ViewController
    // Failing Assertion 
    XCTAssert(viewController != nil, "Test Not Configured Properly")

    uiViewController = anyVC as? UIViewController
    XCTAssert(uiViewController != nil, "Test Not Configured Properly")

  }

I can force the cast with the following lines:

anyVC = storyBoard?.instantiateInitialViewController()
viewController = (anyVC != nil) ? (anyVC  as ViewController) : nil

But this caused the following crash:

libswiftCore.dylib`swift_dynamicCastClassUnconditional:
0x10724f5a0:  pushq  %rbp
0x10724f5a1:  movq   %rsp, %rbp
0x10724f5a4:  pushq  %r14
0x10724f5a6:  pushq  %rbx
0x10724f5a7:  movq   %rsi, %rbx
0x10724f5aa:  movq   %rdi, %r14
0x10724f5ad:  testq  %r14, %r14
0x10724f5b0:  je     0x10724f5de               ; swift_dynamicCastClassUnconditional + 62
0x10724f5b2:  movabsq $-0x7fffffffffffffff, %rax
0x10724f5bc:  andq   %r14, %rax
0x10724f5bf:  jne    0x10724f5de               ; swift_dynamicCastClassUnconditional + 62
0x10724f5c1:  movq   %r14, %rdi
0x10724f5c4:  callq  0x107279a6e               ; symbol stub for: object_getClass
0x10724f5c9:  nopl   (%rax)
0x10724f5d0:  cmpq   %rbx, %rax
0x10724f5d3:  je     0x10724f5ed               ; swift_dynamicCastClassUnconditional + 77
0x10724f5d5:  movq   0x8(%rax), %rax
0x10724f5d9:  testq  %rax, %rax
0x10724f5dc:  jne    0x10724f5d0               ; swift_dynamicCastClassUnconditional + 48
0x10724f5de:  leaq   0x3364d(%rip), %rax       ; "Swift dynamic cast failed"
0x10724f5e5:  movq   %rax, 0xa456c(%rip)       ; gCRAnnotations + 8
0x10724f5ec:  int3   
0x10724f5ed:  movq   %r14, %rax
0x10724f5f0:  popq   %rbx
0x10724f5f1:  popq   %r14
0x10724f5f3:  popq   %rbp
0x10724f5f4:  retq   
0x10724f5f5:  nopw   %cs:(%rax,%rax)

I've also successfully instantiated the ViewController directly but that doesn't do the IBOutlet processing, which is one of the purposes of my tests, to make sure I don't break the linking by renaming things, deleting connections in the Storyboard editor, or the many other ways I have found to break things ...

EDIT ---- I started with a fresh project, chose iOS Application -> Single View Application template.

Replaced the testExample with the code as shown below, Added ViewController to the test target. Similar results. This template has a single view controller of type ViewController, nothing else in the storyboard.

  func testExample() {


      var storyBoard: UIStoryboard?
      var anyVC: AnyObject?
      var viewController: ViewController?

      storyBoard = UIStoryboard(name:"Main", bundle: nil)
      XCTAssert(storyBoard != nil, "Test Not Configured Properly")

      anyVC = storyBoard?.instantiateInitialViewController()
      viewController = anyVC as? ViewController
      XCTAssert(viewController != nil, "Test Not Configured Properly")

      // This is an example of a functional test case.
      XCTAssert(true, "Pass")

    }

The following lldb output at a break point just after the value of anyVC is set:

(lldb) po anyVC
(instance_type = Builtin.RawPointer = 0x00007fe22c92a290 -> 0x000000010e20bd80 (void *)0x000000010e20bea0: OBJC_METACLASS_$__TtC22TestingViewControllers14ViewController)
 {
  instance_type = 0x00007fe22c92a290 -> 0x000000010e20bd80 (void *)0x000000010e20bea0: OBJC_METACLASS_$__TtC22TestingViewControllers14ViewController
} 

Answer

Mike Cole picture Mike Cole · Aug 19, 2014

I came up with a better solution than making everything public. You actually just need to use a storyboard that comes from the test bundle instead of using nil (forcing it to come from the main target's bundle).

var storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: NSBundle(forClass: self.dynamicType))
vc = storyboard.instantiateViewControllerWithIdentifier("LoginVC") as LoginViewController
vc.loadView()