Writing Testable Code

Transcript

1. Writing Testable Code 1 — @basthomas

2. Tests, what are they good for? 2 — @basthomas

3. What do you want to verify? 3 — @basthomas

4. How do you want to verify it? 4 — @basthomas

5. Dependency injection: three ways 5 — @basthomas

6. class Network { let urlSession: URLSession init(urlSession: URLSession = .shared)

   { self.urlSession = urlSession } } 6 — @basthomas

7. class Network { var urlSession = URLSession.shared } 7 —

   @basthomas

8. class Network { func request(using urlSession: URLSession = .shared) {

   } } 8 — @basthomas

9. Mocking through Protocols 9 — @basthomas

10. protocol UIApplicationProtocol { func canOpenURL(_ url: URL) -> Bool func

    open( _ url: URL, options: [UIApplication.OpenExternalURLOptionsKey : Any], completionHandler completion: ((Bool) -> Void)? ) } extension UIApplication: UIApplicationProtocol {} 10 — @basthomas

11. Mocking through Subclassing 11 — @basthomas

12. class URLSessionDataTaskMock: URLSessionDataTask { private let closure: () -> Void

    init(closure: @escaping () -> Void) { self.closure = closure } override func resume() { closure() } } 12 — @basthomas

13. class URLSessionMock: URLSession { var data: Data? var error: Error?

    override func dataTask( with url: URL, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void ) -> URLSessionDataTask { let data = self.data let error = self.error return URLSessionDataTaskMock { completionHandler(data, nil, error) } } } 13 — @basthomas

14. Custom asserts 14 — @basthomas

15. func assertManyThings( cookie: Cookie, file: StaticString = #file, line: UInt

    = #line ) { XCTAssertTrue(cookie.isDoughy, file: file, line: line) XCTAssertLessThan(cookie.calories, 200, file: file, line: line) } 15 — @basthomas

16. XCTest 16 — @basthomas

17. XCTUnwrap XCTNoThrow 17 — @basthomas

18. Let's talk about "flaky" 18 — @basthomas

19. 19 — @basthomas

20. Make sure your architecture takes testability into account 20 —

    @basthomas

21. Tests, Code, Documentation 21 — @basthomas

22. Treat your test code like your real code 22 —

    @basthomas

23. Reviews of tests, not reviews with tests 23 — @basthomas

24. "Your" turn: let's take a look at something you want

    to have covered with tests 24 — @basthomas