Property-Based Testing in Objective-C & Swift with Fox
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The document discusses testing approaches for imperative and functional programming. For imperative programming, tests typically follow the arrange-act-assert pattern and set up object state. For functional programming, tests can be simpler since functions are pure without side effects. Property-based testing with frameworks like QuickCheck and Fox is introduced, which generates random test values rather than writing specific tests. This allows the framework to thoroughly test functions by finding edge cases automatically. An example using Fox to test functions from the Archimedes geometry library in Objective-C is provided.
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Property-Based Testing in Objective-C & Swift with Fox
- 1. brian gesiak @modocache - Born in Greenpoint - Some of you may know me from the Internet
- 2. - Quick
- 3. - Consumers include CapitalOne, GitHub, Artsy, open source projects…
- 4. brian gesiak @modocache - Also iOS Core Systems at Facebook
- 5. functional programming in swift - Excited by interest
- 6. class Banana { // ... func peel() { peeled = true } } - Still write code like Obj-C, embarrassing
- 7. imperative programming - Learn from new field (to me) - Bring it back to my day job
- 8. functional programming imperative programming - Learn from new field (to me) - Bring it back to my day job
- 9. functional programming imperative programming - Learn from new field (to me) - Bring it back to my day job
- 10. testing - In particular - Let’s make sure we’re on same page - How many people here have written a unit test?
- 11. why test? - Confirm app does what you think it does
- 12. - Imperative tests follow basic pattern - Set up state, make state change, confirm state change
- 13. arrange act assert - Imperative tests follow basic pattern - Set up state, make state change, confirm state change
- 14. class BananaTests: XCTestCase { var banana: Banana! override func setUp() { // Arrange: Prepare necessary objects, state banana = Banana(delicious: true) } func testPeelRemovesPeel() { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action XCTAssert(banana.peeled) } } - Makes sense with stateful code (explain peel) - Frameworks like XCTest evolved to help build state
- 15. class BananaTests: XCTestCase { var banana: Banana! override func setUp() { // Arrange: Prepare necessary objects, state banana = Banana(delicious: true) } func testPeelRemovesPeel() { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action XCTAssert(banana.peeled) } } - Makes sense with stateful code (explain peel) - Frameworks like XCTest evolved to help build state
- 16. class BananaTests: XCTestCase { var banana: Banana! override func setUp() { // Arrange: Prepare necessary objects, state banana = Banana(delicious: true) } func testPeelRemovesPeel() { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action XCTAssert(banana.peeled) } } - Makes sense with stateful code (explain peel) - Frameworks like XCTest evolved to help build state
- 17. class BananaTests: XCTestCase { var banana: Banana! override func setUp() { // Arrange: Prepare necessary objects, state banana = Banana(delicious: true) } func testPeelRemovesPeel() { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action XCTAssert(banana.peeled) } } - Makes sense with stateful code (explain peel) - Frameworks like XCTest evolved to help build state
- 18. beforeEach { // Arrange #1: Prepare banana banana = Banana(delicious: true) } describe("peel") { beforeEach { // Arrange #2: More preparation of banana state banana.peeled = false } it("peels the banana") { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action expect(banana.peeled).to(beTrue()) } } - Many frameworks created to build state
- 19. beforeEach { // Arrange #1: Prepare banana banana = Banana(delicious: true) } describe("peel") { beforeEach { // Arrange #2: More preparation of banana state banana.peeled = false } it("peels the banana") { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action expect(banana.peeled).to(beTrue()) } } - Many frameworks created to build state
- 20. beforeEach { // Arrange #1: Prepare banana banana = Banana(delicious: true) } describe("peel") { beforeEach { // Arrange #2: More preparation of banana state banana.peeled = false } it("peels the banana") { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action expect(banana.peeled).to(beTrue()) } } - Many frameworks created to build state
- 21. beforeEach { // Arrange #1: Prepare banana banana = Banana(delicious: true) } describe("peel") { beforeEach { // Arrange #2: More preparation of banana state banana.peeled = false } it("peels the banana") { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action expect(banana.peeled).to(beTrue()) } } - Many frameworks created to build state
- 22. beforeEach { // Arrange #1: Prepare banana banana = Banana(delicious: true) } describe("peel") { beforeEach { // Arrange #2: More preparation of banana state banana.peeled = false } it("peels the banana") { // Act: Perform an action with side effects banana.peel() // Assert: Confirm the effects of that action expect(banana.peeled).to(beTrue()) } } - Many frameworks created to build state
- 23. what’s different in functional programming? - FP prefers immutable objects and pure functions
- 24. func peel(banana: Banana) -> PeeledBanana { return PeeledBanana(delicious: banana.delicious) } - Here’s a pure version of peel
- 25. class PeelTests: XCTestCase { func testPeelReturnsPeeledBanana() { // Assert: Peeled banana is equally delicious let banana = Banana(delicious: false) let peeledBanana = peel(banana) XCTAssertFalse(peeledBanana.delicious) } } - FP uses simple data structures, don’t need setup - Pure functions have no side effects, no act step - One line
- 26. class PeelTests: XCTestCase { func testPeelReturnsPeeledBanana() { // Assert: Peeled banana is equally delicious let banana = Banana(delicious: false) let peeledBanana = peel(banana) XCTAssertFalse(peeledBanana.delicious) } } - FP uses simple data structures, don’t need setup - Pure functions have no side effects, no act step - One line
- 27. class PeelTests: XCTestCase { func testPeelReturnsPeeledBanana() { // Assert: Peeled banana is equally delicious let banana = Banana(delicious: false) let peeledBanana = peel(banana) XCTAssertFalse(peeledBanana.delicious) } } - FP uses simple data structures, don’t need setup - Pure functions have no side effects, no act step - One line
- 28. class PeelTests: XCTestCase { func testPeelReturnsPeeledBanana() { // Assert: Peeled banana is equally delicious let banana = Banana(delicious: false) let peeledBanana = peel(banana) XCTAssertFalse(peeledBanana.delicious) } } - FP uses simple data structures, don’t need setup - Pure functions have no side effects, no act step - One line
- 29. functional programming: spend less time worrying about state - That’s the big sell of functional programming
- 30. xUnit and xSpec are out of date - Solving the wrong problem—don’t need setup/teardown - Haskell has HUnit and hspec, but they’re minor
- 31. QuickCheck - Instead, FP focuses on a different problem, solved by QuickCheck
- 32. class PeelTests: XCTestCase { func testPeelReturnsPeeledBanana() { // Assert: Peeled banana is equally delicious XCTAssertFalse(peel(Banana(delicious: false)).delicious) XCTAssert(peel(Banana(delicious: true)).delicious) } } - To illustrate look at peel() again - Tested false, how about true? - Two params may be OK, but Int?
- 33. class PeelTests: XCTestCase { func testPeelReturnsPeeledBanana() { // Assert: Peeled banana is equally delicious XCTAssertFalse(peel(Banana(delicious: false)).delicious) XCTAssert(peel(Banana(delicious: true)).delicious) } } - To illustrate look at peel() again - Tested false, how about true? - Two params may be OK, but Int?
- 34. func testPeelReturnsPeeledBananaWithSameWeight() { // Test base case XCTAssertEqual(peel(Banana(weight: 2)).weight, 2) // Test some edge cases XCTAssertEqual(peel(Banana(weight: 0)).weight, 0) XCTAssertEqual(peel(Banana(weight: -1)).weight, -1) } - Up to us to determine what to test - These are example-based tests - Helps us think about edge cases (but we think of them)
- 35. func testPeelReturnsPeeledBananaWithSameWeight() { // Test base case XCTAssertEqual(peel(Banana(weight: 2)).weight, 2) // Test some edge cases XCTAssertEqual(peel(Banana(weight: 0)).weight, 0) XCTAssertEqual(peel(Banana(weight: -1)).weight, -1) } - Up to us to determine what to test - These are example-based tests - Helps us think about edge cases (but we think of them)
- 36. QuickCheck - Solves this problem - Basic idea…
- 37. don’t write tests generate them - Fox will throw tons of random data at your function, expecting core properties to hold - Ported to many languages, and now ObjC and Swift
- 38. Fox - Written by Jeff Hui from Pivotal Labs
- 39. property-based testing - QuickCheck and Fox are property-based testing frameworks - What is a property?
- 40. class BananaTests: XCTestCase { func testPeelReturnsPeeledBanana() { let property = forAll(integer()) { weight in let banana = Banana(weight: weight as Int) let peeled = peel(banana) return peeled.weight == banana.weight } Fox.Assert(property) } } - Given any integer - Fox finds the edge cases for us
- 41. class BananaTests: XCTestCase { func testPeelReturnsPeeledBanana() { let property = forAll(integer()) { weight in let banana = Banana(weight: weight as Int) let peeled = peel(banana) return peeled.weight == banana.weight } Fox.Assert(property) } } - Given any integer - Fox finds the edge cases for us
- 42. class BananaTests: XCTestCase { func testPeelReturnsPeeledBanana() { let property = forAll(integer()) { weight in let banana = Banana(weight: weight as Int) let peeled = peel(banana) return peeled.weight == banana.weight } Fox.Assert(property) } } - Given any integer - Fox finds the edge cases for us
- 43. class BananaTests: XCTestCase { func testPeelReturnsPeeledBanana() { let property = forAll(integer()) { weight in let banana = Banana(weight: weight as Int) let peeled = peel(banana) return peeled.weight == banana.weight } Fox.Assert(property) } } - Given any integer - Fox finds the edge cases for us
- 44. class BananaTests: XCTestCase { func testPeelReturnsPeeledBanana() { let property = forAll(integer()) { weight in let banana = Banana(weight: weight as Int) let peeled = peel(banana) return peeled.weight == banana.weight } Fox.Assert(property) } } - Given any integer - Fox finds the edge cases for us
- 45. class BananaTests: XCTestCase { func testPeelReturnsPeeledBanana() { let property = forAll(integer()) { weight in let banana = Banana(weight: weight as Int) let peeled = peel(banana) return peeled.weight == banana.weight } Fox.Assert(property) } } - Given any integer - Fox finds the edge cases for us
- 46. github/Archimedes Geometry functions for Cocoa and Cocoa Touch - Let’s use GitHub’s Archimedes as an example - It’s ObjC but we can use Fox
- 47. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); - Archimedes defines insets—like padding for a view
- 48. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); 10 5 5 10 - Archimedes defines insets—like padding for a view
- 49. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); NSString *string = NSStringFromMEDEdgeInsets(insets); // => @"{10, 5, 10, 5}" NSString *string = @"{1, 2, 3, 4}"; MEDEdgeInsets insets = MEDEdgeInsetsFromString(string); // => MEDEdgeInsets(1, 2, 3, 4) - Contains functions to convert between insets and strings
- 50. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); NSString *string = NSStringFromMEDEdgeInsets(insets); // => @"{10, 5, 10, 5}" NSString *string = @"{1, 2, 3, 4}"; MEDEdgeInsets insets = MEDEdgeInsetsFromString(string); // => MEDEdgeInsets(1, 2, 3, 4) - Contains functions to convert between insets and strings
- 51. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); NSString *string = NSStringFromMEDEdgeInsets(insets); // => @"{10, 5, 10, 5}" NSString *string = @"{1, 2, 3, 4}"; MEDEdgeInsets insets = MEDEdgeInsetsFromString(string); // => MEDEdgeInsets(1, 2, 3, 4) - Contains functions to convert between insets and strings
- 52. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); NSString *string = NSStringFromMEDEdgeInsets(insets); // => @"{10, 5, 10, 5}" NSString *string = @"{1, 2, 3, 4}"; MEDEdgeInsets insets = MEDEdgeInsetsFromString(string); // => MEDEdgeInsets(1, 2, 3, 4) - Contains functions to convert between insets and strings
- 53. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); NSString *string = NSStringFromMEDEdgeInsets(insets); // => @"{10, 5, 10, 5}" NSString *string = @"{1, 2, 3, 4}"; MEDEdgeInsets insets = MEDEdgeInsetsFromString(string); // => MEDEdgeInsets(1, 2, 3, 4) - Contains functions to convert between insets and strings
- 54. MEDEdgeInsets insets = MEDEdgeInsetsMake(10, 5, 10, 5); NSString *string = NSStringFromMEDEdgeInsets(insets); // => @"{10, 5, 10, 5}" NSString *string = @"{1, 2, 3, 4}"; MEDEdgeInsets insets = MEDEdgeInsetsFromString(string); // => MEDEdgeInsets(1, 2, 3, 4) - Contains functions to convert between insets and strings
- 55. it(@"should create a string from an MEDEdgeInsets", ^{ expect(NSStringFromMEDEdgeInsets(insets)).to( equal(@"{1, 2, 3, 4}”)); expect(NSStringFromMEDEdgeInsets(insets2)).to( equal(@"{1.05, 2.05, 3.05, 4.05}”)); }); - Archimedes has example-based tests - Why 1, 2, 3, 4? No real reason. - Someone assumed these were good enough
- 56. it(@"should create a string from an MEDEdgeInsets", ^{ expect(NSStringFromMEDEdgeInsets(insets)).to( equal(@"{1, 2, 3, 4}”)); expect(NSStringFromMEDEdgeInsets(insets2)).to( equal(@"{1.05, 2.05, 3.05, 4.05}”)); }); - Archimedes has example-based tests - Why 1, 2, 3, 4? No real reason. - Someone assumed these were good enough
- 57. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 58. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 59. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 60. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 61. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 62. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 63. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - Given 4 random numbers, we can convert to string and back
- 64. MEDEdgeInsets MEDEdgeInsetsFromString(NSString *string) { int top = 0, left = 0, bottom = 0, right = 0; sscanf(string.UTF8String, "{%d, %d, %d, %d}”, &top, &left, &bottom, &right); return MEDEdgeInsetsMake((CGFloat)top, (CGFloat)left (CGFloat)bottom, (CGFloat)right); } - Let’s say there was a bug in function to convert string to insets
- 65. MEDEdgeInsets MEDEdgeInsetsFromString(NSString *string) { int top = 0, left = 0, bottom = 0, right = 0; sscanf(string.UTF8String, "{%d, %d, %d, %d}”, &top, &left, &bottom, &right); return MEDEdgeInsetsMake((CGFloat)top, (CGFloat)left (CGFloat)bottom, (CGFloat)right); } - Let’s say there was a bug in function to convert string to insets
- 66. {126.0, -299.0, 16.0, 75.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 67. {126.0, -299.0, 16.0, 75.0} => {126.0, -299.0, 16.0, 75.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 68. {126.0, -299.0, 16.0, 75.0} => {9.87, 0.52, -4.21, 26.0} => {9.0, 0.0, -4.0, 26.0} {126.0, -299.0, 16.0, 75.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 69. {126.0, -299.0, 16.0, 75.0} => {9.87, 0.52, -4.21, 26.0} => {9.0, 0.0, -4.0, 26.0} {126.0, -299.0, 16.0, 75.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 70. {126.0, -299.0, 16.0, 75.0} => {9.87, 0.52, -4.21, 26.0} => {9.0, 0.0, -4.0, 26.0} {126.0, -299.0, 16.0, 75.0} {4.93, 0.26, -2.10, 13.0} => {4.0, 0.0, -2.0, 13.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 71. {126.0, -299.0, 16.0, 75.0} => {9.87, 0.52, -4.21, 26.0} => {9.0, 0.0, -4.0, 26.0} {126.0, -299.0, 16.0, 75.0} {4.93, 0.26, -2.10, 13.0} => {4.0, 0.0, -2.0, 13.0} {2.46, 0.13, -1.05, 6.5} => {-2.0, 0.0, -1.0, 6.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 72. {126.0, -299.0, 16.0, 75.0} => {9.87, 0.52, -4.21, 26.0} => {9.0, 0.0, -4.0, 26.0} {126.0, -299.0, 16.0, 75.0} {4.93, 0.26, -2.10, 13.0} => {4.0, 0.0, -2.0, 13.0} {2.46, 0.13, -1.05, 6.5} => {-2.0, 0.0, -1.0, 6.0} ... {0.1, 0.0, 0.0, 0.0} => {0.0, 0.0, 0.0, 0.0} - Fox will find a failure - Then it shrinks to find the smallest failing case
- 73. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - So when you run the test, it’s easier to interpret failure - Property-based tests are powerful - Can use in tandem with example-based tests
- 74. it(@"should convert between MEDEdgeInsets and strings", ^{ id<FOXGenerator> floats = FOXTuple( @[FOXFloat(), FOXFloat(), FOXFloat(), FOXFloat()]); FOXAssert(forAll(floats, ^BOOL(NSArray *generated) { MEDEdgeInsets insets = MEDEdgeInsetsMake( Property failed with (0.1, 0.0, 0.0, 0.0) [generated[0] floatValue], [generated[1] floatValue], [generated[2] floatValue], [generated[3] floatValue]); NSString *string = NSStringFromMEDEdgeInsets(insets); MEDEdgeInsets backToInsets = MEDEdgeInsetsFromString(string); return MEDEdgeInsetsEqualToEdgeInsets(insets, backToInsets); })); }); - So when you run the test, it’s easier to interpret failure - Property-based tests are powerful - Can use in tandem with example-based tests
- 75. test stateful code - Not only can be used together with example-based tests - Can also test stateful things like view controllers
- 76. - We can use Fox
- 77. - We can use Fox
- 78. state - Model changes in state using transitions - Transitions have corresponding “model state” updates - Specify conditions that must be met after transition
- 79. state more transition less transition - Model changes in state using transitions - Transitions have corresponding “model state” updates - Specify conditions that must be met after transition
- 80. state count more transition count + 1 less transition count - 1 - Model changes in state using transitions - Transitions have corresponding “model state” updates - Specify conditions that must be met after transition
- 81. state count property more transition count + 1 property less transition count - 1 - Model changes in state using transitions - Transitions have corresponding “model state” updates - Specify conditions that must be met after transition
- 82. initial count = 0 - Fox will run transitions at random, checking that properties hold
- 83. initial count = 0 more count = 1 property less count = 0 property - Fox will run transitions at random, checking that properties hold
- 84. initial count = 0 more count = 1 property less count = 0 property more count = 1 more count = 2 - Fox will run transitions at random, checking that properties hold
- 85. let moreTransition = FOXTransition(action: { state, _ in let controller = state as BananaViewController controller.moreButton.sendActionsForControlEvents( UIControlEvents.TouchUpInside) }, nextModelState: { modelState, _ in return (modelState as Int) + 1 }) - Fox gives us a hook to move into the next state - And we need to update our model state as well
- 86. let moreTransition = FOXTransition(action: { state, _ in let controller = state as BananaViewController controller.moreButton.sendActionsForControlEvents( UIControlEvents.TouchUpInside) }, nextModelState: { modelState, _ in return (modelState as Int) + 1 }) - Fox gives us a hook to move into the next state - And we need to update our model state as well
- 87. let moreTransition = FOXTransition(action: { state, _ in let controller = state as BananaViewController controller.moreButton.sendActionsForControlEvents( UIControlEvents.TouchUpInside) }, nextModelState: { modelState, _ in return (modelState as Int) + 1 }) - Fox gives us a hook to move into the next state - And we need to update our model state as well
- 88. let moreTransition = FOXTransition(action: { state, _ in let controller = state as BananaViewController controller.moreButton.sendActionsForControlEvents( UIControlEvents.TouchUpInside) }, nextModelState: { modelState, _ in return (modelState as Int) + 1 }) - Fox gives us a hook to move into the next state - And we need to update our model state as well
- 89. let moreTransition = FOXTransition(action: { state, _ in let controller = state as BananaViewController controller.moreButton.sendActionsForControlEvents( UIControlEvents.TouchUpInside) }, nextModelState: { modelState, _ in return (modelState as Int) + 1 }) - Fox gives us a hook to move into the next state - And we need to update our model state as well
- 90. let moreTransition = FOXTransition(action: { state, _ in let controller = state as BananaViewController controller.moreButton.sendActionsForControlEvents( UIControlEvents.TouchUpInside) }, nextModelState: { modelState, _ in return (modelState as Int) + 1 }) - Fox gives us a hook to move into the next state - And we need to update our model state as well
- 91. moreTransition.postcondition = { (modelState, _, subject, _, _) in let controller = subject as BananaViewController return modelState as Int == controller.bananaCount } - Post condition (or property) is must be fulfilled after every transition—that view controller displays correct model state - We can only tap more when count < 10
- 92. moreTransition.postcondition = { (modelState, _, subject, _, _) in let controller = subject as BananaViewController return modelState as Int == controller.bananaCount } - Post condition (or property) is must be fulfilled after every transition—that view controller displays correct model state - We can only tap more when count < 10
- 93. moreTransition.postcondition = { (modelState, _, subject, _, _) in let controller = subject as BananaViewController return modelState as Int == controller.bananaCount } - Post condition (or property) is must be fulfilled after every transition—that view controller displays correct model state - We can only tap more when count < 10
- 94. moreTransition.postcondition = { (modelState, _, subject, _, _) in let controller = subject as BananaViewController return modelState as Int == controller.bananaCount } moreTransition.precondition = { modelState in return (modelState as Int) < 10 } - Post condition (or property) is must be fulfilled after every transition—that view controller displays correct model state - We can only tap more when count < 10
- 95. moreTransition.postcondition = { (modelState, _, subject, _, _) in let controller = subject as BananaViewController return modelState as Int == controller.bananaCount } moreTransition.precondition = { modelState in return (modelState as Int) < 10 } - Post condition (or property) is must be fulfilled after every transition—that view controller displays correct model state - We can only tap more when count < 10
- 96. let stateMachine = FOXFiniteStateMachine( initialModelState: 0) stateMachine.addTransition(moreTransition) stateMachine.addTransition(lessTransition) let executedCommands = executeCommands(stateMachine) { let storyboard = UIStoryboard(name: "Main", bundle: nil) let controller = storyboard.instantiateInitialViewController() as BananaViewController let _ = controller.view return controller } Fox.Assert(forAll(executedCommands) { commands in return executedSuccessfully(commands as NSArray) }) - Same gist for less transition - Define state machine with initial model state - Provide initial state with executeCommands - Minimum failing case displayed
- 97. let stateMachine = FOXFiniteStateMachine( initialModelState: 0) stateMachine.addTransition(moreTransition) stateMachine.addTransition(lessTransition) let executedCommands = executeCommands(stateMachine) { let storyboard = UIStoryboard(name: "Main", bundle: nil) let controller = storyboard.instantiateInitialViewController() as BananaViewController let _ = controller.view return controller } Fox.Assert(forAll(executedCommands) { commands in return executedSuccessfully(commands as NSArray) }) - Same gist for less transition - Define state machine with initial model state - Provide initial state with executeCommands - Minimum failing case displayed
- 98. let stateMachine = FOXFiniteStateMachine( initialModelState: 0) stateMachine.addTransition(moreTransition) stateMachine.addTransition(lessTransition) let executedCommands = executeCommands(stateMachine) { let storyboard = UIStoryboard(name: "Main", bundle: nil) let controller = storyboard.instantiateInitialViewController() as BananaViewController let _ = controller.view return controller } Fox.Assert(forAll(executedCommands) { commands in return executedSuccessfully(commands as NSArray) }) - Same gist for less transition - Define state machine with initial model state - Provide initial state with executeCommands - Minimum failing case displayed
- 99. let stateMachine = FOXFiniteStateMachine( initialModelState: 0) stateMachine.addTransition(moreTransition) stateMachine.addTransition(lessTransition) let executedCommands = executeCommands(stateMachine) { let storyboard = UIStoryboard(name: "Main", bundle: nil) let controller = storyboard.instantiateInitialViewController() as BananaViewController let _ = controller.view return controller } Fox.Assert(forAll(executedCommands) { commands in return executedSuccessfully(commands as NSArray) }) - Same gist for less transition - Define state machine with initial model state - Provide initial state with executeCommands - Minimum failing case displayed
- 100. let stateMachine = FOXFiniteStateMachine( initialModelState: 0) stateMachine.addTransition(moreTransition) stateMachine.addTransition(lessTransition) let executedCommands = executeCommands(stateMachine) { let storyboard = UIStoryboard(name: "Main", bundle: nil) let controller = storyboard.instantiateInitialViewController() as BananaViewController let _ = controller.view return controller } Fox.Assert(forAll(executedCommands) { commands in return executedSuccessfully(commands as NSArray) }) - Same gist for less transition - Define state machine with initial model state - Provide initial state with executeCommands - Minimum failing case displayed
- 101. github.com/jeffh/Fox fox-testing.readthedocs.org/ - That’s Fox in a nutshell; Many more features, see GitHub - Property-based testing is deep, many resources available - Fox will continue to grow, perhaps provide properties
- 102. functional programming imperative programming - QuickCheck has been around since 1999, only in ObjC/Swift recently - Great example of cross-pollination of ideas, excited for more
- 103. brian gesiak @modocache - Thanks for listening. Questions?