How to setup a UIViewController and test it with Unit Test (Swift 3)

MyProjectTests.swift

import XCTest
@testable import MyProject

class MyProjectTests: XCTestCase {
    
    var mainvc: MyProject.ViewController!
    
    private func setUpViewControllers() {
        let storyboard = UIStoryboard(name: "Main", bundle: Bundle.main)
        
        self.mainvc = storyboard.instantiateViewControllerWithIdentifier("MainVC") as! MyProject.ViewController // 
        self.mainvc.loadView()
        self.mainvc.viewDidLoad()
    }
    
    override func setUp() {
        super.setUp()

        self.setUpViewControllers()
    }
    
    override func tearDown() {
        mainvc = nil
        
        super.tearDown()
    }
    
    func testMainVC() {
        XCTAssertNotNil(self.mainvc, "Main VC is nil")
        XCTAssertNotNil(self.mainvc.button, "Button is nil")
    }
}