JohnSundell

struct Post {
    class TextFormatter {
        enum Option {
            case highlightNames
            case highlightLinks
        }

        private let options: Set<Option>

        init(options: Set<Option>) {

JohnSundell

struct Post {
    class TextFormatter {
        enum Option {
            case highlightNames
            case highlightLinks
        }

        private let options: Set<Option>

        init(options: Set<Option>) {

JohnSundell

struct Post {
    let id: Int
    let author: User
    let title: String
    let text: String
}

class PostTextFormatter {
    private let options: Set<Option>

JohnSundell

extension Command {
    enum Error: Swift.Error {
        case missing
        case invalid(String)
    }
}

JohnSundell

func testLoadingData() {
    class NetworkEngineMock: NetworkEngine {
        typealias Handler = NetworkEngine.Handler 
        
        var requestedURL: URL?
        
        func performRequest(for url: URL, completionHandler: @escaping Handler) {
            requestedURL = url
            
            let data = “Hello world”.data(using: .utf8)

JohnSundell

class DataLoader {
    enum Result {
        case data(Data)
        case error(Error)
    }
    
    private let engine: NetworkEngine
    
    init(engine: NetworkEngine = URLSession.shared) {
        self.engine = engine

JohnSundell

protocol NetworkEngine {
    typealias Handler = (Data?, URLResponse?, Error?) -> Void
    
    func performRequest(for url: URL, completionHandler: @escaping Handler)
}

extension URLSession: NetworkEngine {
    typealias Handler = NetworkEngine.Handler
    
    func performRequest(for url: URL, completionHandler: @escaping Handler) {

JohnSundell

class DataLoader {
    enum Result {
        case data(Data)
        case error(Error)
    }
    
    func load(from url: URL, completionHandler: @escaping (Result) -> Void) {
        let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
            if let error = error {
                return completionHandler(.error(error))

JohnSundell

class CardGameTests: XCTestCase {
    func testDrawingRandomCard() {
        var randomizationUpperBound: UInt32?
        
        let deck = Deck(cards: [Card(value: .ace, suite: .spades)])
        
        let game = CardGame(deck: deck, randomizer: { upperBound in            
            // Capture the upper bound to be able to assert it later
            randomizationUpperBound = upperBound
            

JohnSundell

class CardGame {
    typealias Randomizer = (UInt32) -> UInt32
    
    private let deck: Deck
    private let randomizer: Randomizer
    
    init(deck: Deck, randomizer: @escaping Randomizer = arc4random_uniform) {
        self.deck = deck
        self.randomizer = randomizer
    }