Swift testing with Protocols

AccountDownloader.swift

import Foundation
import UIKit

protocol DownloadAccountProtocol {
    func downloadAccount(with name: String, completion: (Person) -> ())
}

class ServerDownloader: DownloadAccountProtocol {
    func downloadAccount(with name: String, completion: (Person) -> ()) {
        let personDictionary: [String: String] = [:] // Dictionary JSON downloaded from server
        if let firstName = personDictionary["first_name"], let lastName = personDictionary["last_name"] {
            let personModel = Person(firstName: firstName, lastName: lastName)
            completion(personModel)
        } else {
            completion(Person(firstName: "John", lastName: "Adams"))
        }
    }
}

class DownloadAccountClass {
    
    var downloadedAccount: Person?
    
    init(downloadProtocol: DownloadAccountProtocol) {
        downloadProtocol.downloadAccount(with: "Adam", completion: {value in
            self.downloadedAccount = value
        })
    }
}

FileDownloaderTests.swift

import Foundation
import Quick
import Nimble

@testable import SampleSwiftCode

class DownloadAccountSpec: QuickSpec {
    
    override func spec() {
        describe("Sample testing") {
            it("This test should correctly mock the desired function call", closure: {
                let downloader = DownloadAccountClass(downloadProtocol: DummyAccountDownloader())
                expect(downloader.downloadedAccount?.firstName).to(equal("Gavin"))
                expect(downloader.downloadedAccount?.lastName).to(equal("Belson"))
            })
        }
    }
    
    class DummyAccountDownloader: DownloadAccountProtocol {
        func downloadAccount(with name: String, completion: (Person) -> ()) {
            // This data is being read from the local json file instead of network call
            // Local JSON file
            // { "first_name": "Gavin", "last_name": "Belson" }
            let dummyJsonPersonalData: [String: String] = [:]
            let personModel = Person(firstName: dummyJsonPersonalData["first_name"], lastName: dummyJsonPersonalData["last_name"])
            completion(personModel)
        }
    }
}

RunningExample.swift

let downloader = DownloadAccountClass(downloadProtocol: ServerDownloader())