                                                                                              at: indexPath(0, 0)) is NibHeaderFooterView)
     }
     func testWillDisplayHeaderInSection() {
+        guard #available(iOS 13, tvOS 13, *) else { return }
         let exp = expectation(description: "willDisplayHeaderInSection")
         controller.manager.willDisplayHeaderView(ReactingHeaderFooterView.self, { header, model, section  in
             exp.fulfill()

        case three
    }
    
    var dataSourceReference: UICollectionViewDiffableDataSourceReference!
    var controller = DTCellTestCollectionController()
    
    override func setUp() {
        super.setUp()
        let _ = controller.view
        controller.manager.register(NibCell.self)
        dataSourceReference = controller.manager.configureDiffableDataSource(modelProvider: { $1 })
        controller.manager.register(NibCell.self)
    }
    
    func testMultipleSectionsWorkWithDiffableDataSourceReferences() {
        dataSourceReference.applySnapshot(.snapshot(with: { snapshot in
            snapshot.appendSections(withIdentifiers: [Section.one, Section.two])
            snapshot.appendItems(withIdentifiers: [1,2], intoSectionWithIdentifier: Section.one)

    
    override func setUp() {
        super.setUp()
        guard #available(iOS 13, tvOS 13, *) else { return }
        let _ = controller.view
        controller.manager.register(NibCell.self)
        diffableDataSource = controller.manager.configureDiffableDataSource(modelProvider: { $1 })
        controller.manager.register(NibCell.self)
    }
    
    func testMultipleSectionsWorkWithDiffableDataSources() {
        guard #available(iOS 13, tvOS 13, *) else { return }
        dataSource.apply(.snapshot(with: { snapshot in
            snapshot.appendSections([.one, .two])
            snapshot.appendItems([1,2], toSection: .one)
