How can I assert a delegate is called in my unit test

Question

I would like to asset that the correct delegate method is called depending on the result of a check in my presenter.

Having mocked out my IdentityProvider to return true, how would I write a test to assert delegate?.userIsAuthenticated() is called?

import Foundation
import InjectStory

protocol StartPresenterDelegate: class {
    func userIsAuthenticated()
    func userNeedsToAuthenticate()
}

class StartPresenter {
    weak var delegate: StartPresenterDelegate?
    weak var view: StartViewInterface!

    private lazy var identityProvider = Dependencies.identityProvider.inject()

    init(view: StartViewInterface) {
        self.view = view
    }

    private func checkUserAuthState() {
        if identityProvider.isAuthorized() {
            delegate?.userIsAuthenticated()
        } else {
            delegate?.userNeedsToAuthenticate()
        }
    }

}

extension StartPresenter: StartPresentation {
    func onViewDidLoad() {
        checkUserAuthState()
    }
}

extension StartPresenter {
    struct Dependencies {
        static let identityProvider = Injection<IdentityProviderProtocol>(IdentityProvider.shared)
    }
}

Answer 1

You have to mock the StartPresenterDelegate as follows too.

class MockStartPresenterDelegate: StartPresenterDelegate {
   var userIsAuthenticated_wasCalled = false 

   func userIsAuthenticated() {
       userIsAuthenticated_wasCalled = true
   }
}

Inject MockStartPresenterDelegate as the delegate and check that userIsAuthenticated_wasCalled is true

Answer 2

You need to do some trick. Create MockDelegateClass for your protocol StartPresenterDelegate example:

class MockDelegate: StartPresenterDelegate {

    var isUserIsAuthenticatedCalled = false
    var isUserNeedsToAuthenticateCalled = false

    func userIsAuthenticated() {
        isUserIsAuthenticatedCalled = true
    }

    func userNeedsToAuthenticate() {
        isUserNeedsToAuthenticateCalled = true
    }
}

then in your test try to do something like that:

func test_MyTest() {
    // init your class StartPresenter that you wanna test
    var presenter = StartPresenter(...)
    var mockDelegate = MockDelegate()
    presenter.delegate = mockDelegate
    presenter.onViewDidLoad()

    XCTAssertTrue(mockDelegate.isUserIsAuthenticatedCalled)
    XCTAssertFalse(mockDelegate.isUserNeedsToAuthenticateCalled)
    // or change isUserIsAuthenticatedCalled and isUserNeedsToAuthenticateCalled if you expect another states
}

For different states you need different tests, for you it will be the easiest way to test delegate calling.

Answer 3

In this way you can confirm the unit test for delegates in Swift apps