protocol URLSessionProtocol {
    func dataTask(with urlRequest: URLRequest,  completionHandler: @escaping DataTaskCompletionHandler) -> URLSessionDataTask
}

struct NetworkManager {
    private let urlSession: URLSessionProtocol
    
    // ...
}

// given
// 받아올 데이터를 임의로 생성
let dummy = DummyData(data: data, response: response, error: nil)
let stubUrlSession = StubURLSession(dummy: dummy)
sut = NetworkManager(urlSession: stubURLSession)

// when
sut?.requestData(from: url, completion: { result in
    // then
    // startLoad로 받아온 데이터는 DummyData의 데이터
    XCTAssertEqual(data, dataAsset.data)
    expectation.fulfill()
})

final class BoxOfficeManager {
    private(set) var dailyBoxOffices: [DailyBoxOffice] = []
    
    // ...
    func fetchBoxOffice(completion: @escaping (Bool) -> Void) {
        
        // ...
        networkManager.requestData(from: url) { result in
            switch result {
            case .success(let data):
                do {
                    let boxOffice = try JSONDecoder().decode(BoxOffice.self, from: data)
                    self.dailyBoxOffices = DataManager.boxOfficeTransferDailyBoxOfficeData(boxOffice: boxOffice)
                    completion(true)
                } // ...
            }
        }
    }
}

final class BoxOfficeManager {
    private(set) var dailyBoxOffices: [DailyBoxOffice] = []
    
    // ...
    func fetchBoxOffice(completion: @escaping (Bool) -> Void) {
        
        // ...
        networkManager.requestData(from: url) { [weak self] result in
            guard let self else {
                return
            }
                                               
            switch result {
            case .success(let data):
                do {
                    let boxOffice = try JSONDecoder().decode(BoxOffice.self, from: data)
                    self.dailyBoxOffices = DataManager.boxOfficeTransferDailyBoxOfficeData(boxOffice: boxOffice)
                    completion(true)
                } // ...
            }
        }
    }
}

present(alert, animated: false)

typealias RankStateColor = (targetString: String, color: UIColor)

struct DailyBoxOffice: Hashable {
    let movieCode: String
    let rank: String
    let rankState: String
    let movieTitle: String
    let dailyAndTotalAudience: String
    let rankStateColor: RankStateColor
    
    static func == (lhs: DailyBoxOffice, rhs: DailyBoxOffice) -> Bool {
        return lhs.movieCode == rhs.movieCode
            && lhs.rank == rhs.rank
            && lhs.rankState == rhs.rankState
            && lhs.movieTitle == rhs.movieTitle
            && lhs.dailyAndTotalAudience == rhs.dailyAndTotalAudience
    }
    
    func hash(into hasher: inout Hasher) {
        hasher.combine(movieCode)
        hasher.combine(rank)
        hasher.combine(rankState)
        hasher.combine(movieTitle)
        hasher.combine(dailyAndTotalAudience)
    }
}

protocol ModelDelegate: AnyObject {}

class Model {
    var delegate: ModelDelegate?
        deinit {
        print("deinit Model")
    }
}

class ViewController: ModelDelegate {
    var model: Model?
    
    deinit {
        print("deinit ViewController")
    }
    
    func start() {
 
        model = Model()
        model?.delegate = self
    }
}

var viewController: ViewController? = ViewController()
viewController?.start()
viewController = nil

protocol ModelDelegate: AnyObject {}

class Model {
    weak var delegate: ModelDelegate?
        deinit {
        print("deinit Model")
    }
}

class ViewController: ModelDelegate {
    var model: Model?
    
    deinit {
        print("deinit ViewController")
    }
    
    func start() {
 
        model = Model()
        model?.delegate = self
    }
}

var viewController: ViewController? = ViewController()
viewController?.start()
viewController = nil

// deinit ViewController
// deinit Model

final class CalendarViewController: UIViewController {
    weak var delegate: CalendarViewControllerDelegate?
    
    // ...
}

switch collectionViewMode {
case .list:
    collectionView.setCollectionViewLayout(listLayout(), animated: true)
case .grid:
    collectionView.setCollectionViewLayout(gridLayout(), animated: true)
}

var snapshot = NSDiffableDataSourceSnapshot<Section, DailyBoxOffice>()
snapshot.appendSections([.main])
snapshot.appendItems(boxOfficeManager.dailyBoxOffices, toSection: .main)
snapshot.reloadSections([.main])

dailyBoxOfficeDataSource.apply(snapshot, animatingDifferences: true)

let titleLabelConstraint = titleLabel.widthAnchor.constraint(equalTo: titleLabel.heightAnchor, multiplier: 3)
titleLabel.setContentCompressionResistancePriority(.required, for: .vertical)