Sample iOS Unit Tests: Testing a Segue is called using a Mock UIViewController

Sample iOS Unit Tests: Testing a Segue is called using a Mock UIViewController

   
   // Sample 1: Calling segue to transition to another ViewController by tapping a UICollectionView cell
   
   func testSUT_CanTransitionToTargetViewController_WhenCollectionViewCellTapped() {
        
        // declare mock
        class MockViewController: ViewController {
            var segueIdentifier: NSString?
            override private func performSegueWithIdentifier(identifier: String, sender: AnyObject?) {
                segueIdentifier = identifier
            }
        }
        
        // instantiate mock
        let mockViewController = MockViewController()
        
        // assign a place array to mock (instead of calling network) - so the CollectionView has data
        let responseArray = [
            [
                "id": 16202,
                "lat": 42.1172689197255,
                "lng": -70.9595081595093,
                "name": "Abington",
                "state": "Massachusetts",
                "image": "https://s3.amazonaws.com/to-app-photos/place-null.png",
                "bestfits": 0,
                "favorite": false,
                "dismissed": false
            ],
            [
                "id": 16750,
                "lat": 39.4250075233965,
                "lng": -74.4990416738654,
                "name": "Absecon",
                "state": "New Jersey",
                "image": "https://s3.amazonaws.com/to-app-photos/place-null.png",
                "bestfits": 0,
                "favorite": false,
                "dismissed": false
            ]
        ]
        mockViewController.items = responseArray
        
        // simulate tapping collection view cell
        mockViewController.collectionView(systemUnderTest.collectionView, didSelectItemAtIndexPath: NSIndexPath(forRow: 0, inSection: 0))

        // confirm segue was called
        let expectedSegueIdentifier = "toDetailsVC" // target segue identifier 
        let actualSequeIdentifier = mockViewController.segueIdentifier
        XCTAssertEqual(expectedSegueIdentifier, actualSequeIdentifier)
    }
    
   // Sample 1: Calling segue to transition to another ViewController after logging in
   
    func testSUT_CanTransitionToTargetViewControllerAfterSuccessfulLogin() {
        
        // mock model class provides a successful login
        class MockUser: User {
            override func loginWithUsername(username: String, password: String, completion: (isSuccess: Bool, isNewUser: Bool) -> Void) {
                completion(isSuccess: true, isNewUser: false) 
            }
        }
        
        // mock controller for evaluating what segue identifier was called after calling controller method
        class MockLoginViewController: LoginViewController {
            var segueIdentifier: NSString?
            override func performSegueWithIdentifier(identifier: String, sender: AnyObject?) {
                segueIdentifier = identifier
            }
        }
        
        // LoginVC, SeedUser state
        let mockLoginVC = MockLoginViewController()
        let mockUser = MockUser()
        mockLoginVC.appUser = mockUser
        
        // TextFields have been entered
        let userTextField = UITextField()
        let passwordTextField = UITextField()
        mockLoginVC.userNameTextField = userTextField
        mockLoginVC.passwordTextField = passwordTextField
        mockLoginVC.userNameTextField.text = "bla@email.com"
        mockLoginVC.passwordTextField.text = "bla"
        
        // logging in succeeds
        mockLoginVC.handleLogInTap(UIButton()) // this calls model class to handle login (which will succeed)
        
        // Assertions
        XCTAssertNotNil(mockLoginVC.segueIdentifier)
        
        let expectedSegueIdentifier = "fromLoginVCtoTargetVC" // target segue identifier on successful login
        let actualSequeIdentifier = mockLoginVC.segueIdentifier
        XCTAssertEqual(expectedSegueIdentifier, actualSequeIdentifier)
    }