deinit called but the uint testing not finished - swift

Question

I'm trying to test my coordinator flow but the child coordinator deinit called before the unit test case finished
My coordinator class
public final class AppCoordinator: Coordinator {
public var childCoordinators: [Coordinator] = []
public var navigationController: UINavigationController
var window: UIWindow?
public init(window: UIWindow?) {
self.window = window
let secController = SecController()
self.navigationController = UINavigationController(rootViewController: secController)
secController.delegate = self
}
public func start() {
window?.rootViewController = navigationController
window?.makeKeyAndVisible()
}
}
extension AppCoordinator: SecControllerDelegate, SignInControllerDelegate {
public func removeSingIn() {
self.childCoordinators.removeFirst()
}
public func showSignIn() {
let signInCoordinator = SignInCoordinator(navigationController: self.navigationController)
signInCoordinator.delegate = self
self.childCoordinators.append(signInCoordinator)
signInCoordinator.start()
}
}
Unit test class
class AppCoordinatorTests: XCTestCase {
var coordinator: AppCoordinator!
override func setUp() {
super.setUp()
coordinator = AppCoordinator(window: UIWindow())
}
override func tearDown() {
coordinator = nil
super.tearDown()
}
func testStartMethod() {
coordinator.start()
XCTAssertNotNil(coordinator.window?.rootViewController)
}
func testShowSignIn() {
coordinator.showSignIn()
XCTAssertFalse(coordinator.childCoordinators.isEmpty)
XCTAssertTrue(coordinator.navigationController.visibleViewController is SignInController)
}
}
when try to test testShowSignIn always failed because of the deinit call removeSingIn function
public class SignInController: UIViewController {
public weak var delegate: SignInControllerDelegate?
public init() {
super.init(nibName: nil, bundle: nil)
}
deinit {
self.delegate?.removeSingIn()
}
}

Answer 1

Let's review the steps:
testShowSignIn calls coordinator.showSignIn(), where coordinator is an AppCoordinator.
showSignIn() instantiates a SignInCoordinator, and sets its delegate to the AppCoordinator instance.
Now we reach the important part:
We reach the end of showSignIn(). The SignInCoordinator goes out of scope, so Swift destroys it.
Nothing maintains a reference to the SignInCoordinator. But you want to test the interaction between the AppCoordinator and the SignInCoordinator. The code is fighting you, because AppCoordinator decides to create and destroy the SignInCoordinator on its own.
You can test it by changing the design. You have a couple of options.
Option 1: Change AppCoordinator to have a lazy computed property that returns the SignInCoordinator. This can work if you're okay with that design. Then the SignInCoordinator will continue to live, so that the test can query it. This improves the testability of AppCoordinator by exposing the SignInCoordinator.
Option 2: Have the test create a SignInCoordinator and pass it in as an argument to showSignIn(). Then the SignInCoordinator lifecycle will be managed completely outside of AppCoordinator.