SwityKit

SwityKit is an infrastructure that makes easy unit test writing and aims to increase coverage.

Used with SwityTestGenerator. This xcode source editor extension helps to mock generation.

Benefits

🚀 Generates assertions to the debug log

🚀 Reduces test run time by ~40%

🚀 It prevents us from writing incomplete tests

🚀 Less mock code

🚀 Tests that it is invoked in the correct order.

Installation

Swift Package Manager

To integrate SwityKit into your Xcode project using Swift Package Manager, add it to the dependencies value of your Package.swift:

dependencies: [
    .package(url: "https://github.com/aytugsevgi/SwityKit", from: "1.0.5")
]

You need to add to Build Phases -> Link Binary With Libraries for test targets. Also remove from main target.

Example

Mock

final class MockHomeViewController: HomeViewControllerInterface, MockAssertable {
    typealias MockIdentifier = MockHomeViewControllerElements
    var invokedList: [MockHomeViewControllerElements] = []

    var stubbedPreferredTabBarVisibility: TabBarVisibility!

    var preferredTabBarVisibility: TabBarVisibility {
        invokedList.append(.preferredTabBarVisibility)
        return stubbedPreferredTabBarVisibility
    }

    func viewDidLoad() {
        invokedList.append(.viewDidLoad)
    }
    
    func scroll(to indexPath: IndexPath) {
        invokedList.append(.scroll(to: indexPath))
    }
}

enum MockHomeViewControllerElements: MockEquatable {
    case preferredTabBarVisibility
    case viewDidLoad()
    case scroll(to: IndexPath)
}

Test

final class HomeViewPresenterTests: XCTestCase, BaseTestCaseInterface {
    var mocks: [MockAssertable] { [view, delegate] }
    
    var view: MockHomeViewController!
    var delegate: MockHomeDelegate!
    var presenter: HomeViewPresenter!
    
    override func setUp() {
        super.setUp()
        view = .init()
        delegate = .init()
        presenter = .init(view: view)
    }
    
    override func tearDown() {
        super.tearDown()
        view.assertions("view")
        delegate.assertions("delegate")
        
        view = nil
        delegate = nil
        presenter = nil
    }
    
    func test_viewDidLoad_InvokesRequiredMethods() {
       invokedNothing()
       
       presenter.viewDidLoad()
       
       view.assertInvokes([.preferredTabBarVisibility,
                           .scroll(to: .init(item: 0, section: 1))])
       invokedNothing(excepts: [view])
    }
}

Debug Log (Generation of assertions)

• Manipulating test generation. If you want to change the output of a type, you can write extension with conform CustomStringConvertable.

extension User: CustomStringConvertable {
    public var description: String {
        ".init(name: \"\(self.name)\", age: \"\(self.age)\")"
    }
}

• If that type already conforms to CustomStringConvertable, you just need to override it.

extension NSAttributedString {
    public override var description: String {
        ".init(string: \"\(self.string)\")"
    }
}

Deep Dive

MockAssertable

This protocol must conform to mock classes. With this protocol, the mock class has an array called invokedList. The element of this array is the typealias that is expected to be defined with MockIdentifier.

final class MockHomeViewController: HomeViewControllerInterface, MockAssertable {
    typealias MockIdentifier = MockHomeViewControllerElements
    var invokedList: [MockHomeViewControllerElements] = []
    .
    .
    .

MockIdentifier type must be enum with conformed MockEquatable. Like MockHomeViewControllerElements example above.

enum MockHomeViewControllerElements: MockEquatable {
    ...
}

MockAssertable also has helpful public APIs.

• assertInvokes(): Tests that nothing was invoked from mock.
• assertInvokes(_ givenInvokes: [MockIdentifier]): Tests whether the elements in the array have been invoked. If it is missing or extra, it will give an error. It also warns you if the array is in the wrong order.
• assertions(name: String): Generate assertions to debug log according to invokedList array. If you call on override func tearDown() it's generate correctly after run each test func.
• tearDown(): Deletes all elements of the invokedList array. It continues as nothing was invoked.

MockEquatable

MockEquatable allows us to assert. It allows to get the String describing of the enum case in which it is conformed. Then it looks at the equality of these 2 strings when doing the comparison.

BaseTestCaseInterface

This protocol must conform to test classes. Requests mocks from test class. Like,

final class HomeViewPresenterTests: XCTestCase, BaseTestCaseInterface {
    var mocks: [MockAssertable] { [view, delegate] }
    .
    .
    .

APIs it provides;

• tearDownMocks(): Empties the invokedList array of all mocks. It continues as if nothing was invoked.
• invokedNothing(excepts: [BaseMockAssertable] = .empty): Shortcut assertion. Tests that the given in the test class's mocks array is not invoked at all. Does not check mocks given to excepts.