title: unit testing cell is nil
body: <p><strong><em>Issue:</em></strong></p>
  
  <p>I loaded collectionView with 3 Dummy items. However Cell came back nil, is it because view was never loaded? How do you guys test your collectionViewCell type?</p>
  
  <p><strong><em>Code</em></strong></p>
  
  <pre><code>var window: UIWindow?
  var sut: QuestsDataProvider!
  var collectionView: UICollectionView!
  
  override func setUp() {
      super.setUp()
      bulletinController = BulletinController(collectionViewLayout: UICollectionViewFlowLayout())
      sut = QuestsDataProvider(acceptedQuests: false, completedQuests: false)
      bulletinController.collectionView?.dataSource = sut
      bulletinController.collectionView?.delegate = sut
  
      window = UIWindow()
      window?.makeKeyAndVisible()
      window?.rootViewController = bulletinController
  }
  
  func testCellIsQuestCell() {
      let indexPath = IndexPath(item: 1, section: 0)
      let cell = collectionView.cellForItem(at: indexPath)
      guard let count = sut.questManager?.quests.count else {return XCTFail()}
      XCTAssertTrue(cell is QuestCell)
  }
  </code></pre>
  
  <p>Edit:</p>
  
  <p>Upon Further testing, I'm able to see the dummy Cell inside my simulator and get a accurate count from <code>numberOfitems(InSection: Int)</code>. However I have no visible Cell.</p>
  
  <p>2nd Edit:</p>
  
  <p>After further research, I found out the issue is <code>collectionView.cellForItem(at: indexPath)</code> only shows visible cell. Is there any other method for unit testing collection view cell type?</p>