Sample of Swift property wrappers for unit testing

.swift

import UIKit

@propertyWrapper
struct Printer<T> {
    
    public var currentValue: T?
    
    var wrappedValue: T? {
        get {
            print("Property wrapper value printed", currentValue)
            return currentValue
        }
        
        set {
            currentValue = newValue
        }
    }

    
}

protocol StorageProtocol: class {
    
    var name: String? { get set }
    var surname: String? { get set }
    
}

class Storage: StorageProtocol {
    
    @Printer var name: String?
    @Printer var surname: String?
    
}

class StorageMock: StorageProtocol {
    
    var name: String?
    var surname: String?
        
}

class StorageMockOverride: Storage {
    
    var _name: String?
    var _surname: String?
    
    override var name: String? {
        get {
            return _name
        }
        
        set {
            _name = newValue
        }
    }
    
    override var surname: String? {
        get {
            return _surname
        }
        
        set {
            _surname = newValue
        }
    }
    
}

let storage: StorageProtocol = Storage()

storage.name = "Printable Name"
storage.surname = "Printable Surname"

let storageMock: StorageProtocol = StorageMock()

storageMock.name = "Protocol mock name"
storageMock.surname = "Protocol mock surname"

let storageMockUsingOverride: StorageProtocol = StorageMockOverride()


storageMockUsingOverride.name = "Overriden name"
storageMockUsingOverride.surname = "Overriden surname"


print("Printer sample:", storage.name, storage.surname)
print("Printer mock protocol sample:", storageMock.name, storageMock.surname)
print("Printer mock override sample:", storageMockUsingOverride.name, storageMockUsingOverride.surname)