Mock UNNotificationResponse & UNNotification (and other iOS platform classes with init() marked as unavailable)

To do it you do the following.

Get a real example of the object while debugging and save in file system using your simulator.

func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: (UNNotificationPresentationOptions) -> Void) {

let encodedObject = NSKeyedArchiver.archivedData(withRootObject: notification)

let  path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] + "/notification.mock"

fileManager.createFile(atPath: path, contents: encodedObject, attributes: nil)

Find the object in your Mac and add the file in the same target as the test class.

Now unarchive in your test.

let path = Bundle(for: type(of: self)).path(forResource: "notification", ofType: "mock")

let data = FileManager.default.contents(atPath: path ?? "")

let notification = NSKeyedUnarchiver.unarchiveObject(with: data ?? Data()) as? UNNotification