Rui Peres: Testing FRP Code

2. BUENOS DÍAS BARCELONA !☀# 2
3. FRP && TESTING 3
4. But before we start... 4
5. SMALL STORY... ! 5
6. WAY BACK IN 2013... ⏰ 6
7. FRP + RAC + OBJC ! 7
14. FRP 101 ! 14
15. FAMILIAR CONCEPTS... ! 15
16. KVO + NSOperation + ✨ 16
17. KVO 17
18. MutableProperty<T> 18
19. let foo = MutableProperty(1) // 1. observe foo foo.signalProducer.startWithNext { newFooValue in print(newFooValue) // prints "1" } // 2. modifiy foo's value foo.value = 2 // 3. prints "2" 19
20. NSOperation 20
21. SignalProducer<T, E: ErrorType> 21
22. let networkCall: SignalProducer<NSData, NSError> = ... let parser: NSData -> [Painting] = ... let paintingsProducer = networkCall.map(parser) .startOn(QueueScheduler()) 22
23. paintingsProducer.startWithNext { paintings in print(paintings) // [!, "] } paintingsProducer.on( failure: { error in // handle error }, next: { paintings in print(paintings) // [!, "] }) .start() 23
24. ✨ 24
26. EXAMPLES... ! 26
27. Form Validation 27
29. let email: MutableProperty<String> = emailTextField.rex_text let password: MutableProperty<String> = passwordTextField.rex_text let isValid: (String, String) -> Bool = ... let areCredentialsValid = combineLatest(email.producer, password.producer).map(isValid) loginButton.rex_enabled <~ areCredentialsValid 29
31. Puzzle ! 31
34. A plan... ! 34
36. let drinks = SignalProducer<[String], NoError>(value: ["!","!"]) let areSober: [String] -> Bool = ... let gamePlan = drinks .concat(drinks.delay(7.5)) .concat(timer(5).flatMapLatest { _ in drinks }.takeWhile(areSober)) 36
37. TESTING FRP ! 37
38. Discrete 38
39. func testNumberPaintings() { let expectation = self.expectationWithDescription("Expect to have 2 paintings") defer { self.waitForExpectationsWithTimeout(1.0, handler: nil) } paintingsViewModel.paintingsProducer.startWithNext { paintings in XCTAssertEqual(paintings.count, 2) expectation.fulfill() } } 39
40. func testNumberPaintings() { let result: Result<[Painting], Error>? = paintingsViewModel.paintingsProducer.first() XCTAssertEqual(result?.value?.count, 2) } 40
41. Continuous 41
42. final class StubbedNextValues<T: Equatable> { private var nextValues: [T] private let expectation: XCTestExpectation init(nextValues: [T] , expectation: XCTestExpectation) { self.nextValues = nextValues self.expectation = expectation } func handleNextValue(nextValue: T) -> Void { guard !nextValues.isEmpty else { fatalError("Can't handle \(nextValue)") } let stubbedValue = nextValues.removeFirst() XCTAssertEqual(stubbedValue, nextValue) if nextValues.isEmpty { expectation.fulfill() } } } 42
43. let producer: SignalProducer<Int, NoError> = ... let stubbedNextValues = StubbedNextValues(nextValues: [1, 2, 3, 4], expectation: expectation) producer.startWithNext(stubbed.handleNextValue) 43
44. FRP takes a while to get used to... ! 44
45. ...testing FRP code is as difficult as you want it to be ! 45
46. THANKS @peres 46