FriendsViewController.swift

//
//  FriendsViewController.swift
//  MyPoject

import Foundation
import UIKit
import MapKit

public class FriendsViewController: UIViewController {

    public func include(array: [User], userId: String) -> Bool {
        for item in array {
            if item.userId == userId {
                return true
            }
        }
        return false
    }
}

FriendsViewControllerTest.swift

//  FriendsViewControllerTest.swift
//  MyProject

import UIKit
import XCTest
import MyProject

class FriendsViewControllerTest: XCTestCase {
    
    var viewController: FriendsViewController!
    
    override func setUp() {
        super.setUp()
        // Put setup code here. This method is called before the invocation of each test method in the class.
        self.viewController = FriendsViewController()
        self.viewController.loadView()
    }
    
    override func tearDown() {
        // Put teardown code here. This method is called after the invocation of each test method in the class.
        super.tearDown()
    }
    
    func mockUsers() -> [User]{
        var users = [User(userId: "1", username: "soupguy", gender: 0, name: "Bob"),
            User(userId: "2", username: "breadeater", gender: 1, name: "Alice"),
            User(userId: "3", username: "lawnmowersrule", gender: 0, name: "Alex")]
        return users
    }

    func testInclude() {
        var users = mockUsers()
        XCTAssert(self.viewController.include(users, userId: "2"), "Pass")
    }
}

User.swift

//
//  User.swift
//  MyProject
//

import Foundation

public class User {
    var userId: String
    var username: String
    var name: String
    var gender: Int

    public init(userId: String, username: String, gender: Int, name: String) {
        self.userId = userId
        self.username = username
        self.gender = gender
        self.name = name
    }
}