2013-01-10 iOS testing

Transcript

1. Testing in iOS 10.01.2013 by Tomasz Janeczko
2. About me Tomasz Janeczko • iOS developer in Kainos • Enthusiast of business, electronics, Rails & Heroku • Organizer of first App Camp in UK and PL
3. So let’s talk about testing.
4. Why we test?
6. So?
7. • Reliability • Regression • Confidence (e.g. refactoring)
8. Why not to test?
9. Why not to test? • Heavy dependence on UI • Non-testable code • Bad framework
10. How to address issues • Sample - downloading stuff from interwebz
11. First fault Writing tests after writing code
12. Separation of concerns
13. Separation of concerns • Let’s separate out the UI code • Same for services interaction
14. Demo of tests
15. Writing tests Meet Kiwi and OCMock
16. Kiwi • RSpec-like tests writing • Matchers • Cleaner and more self-descriptive code
17. Kiwi describe(@"Tested class", ^{ context(@"When created", ^{ it(@"should not fail", ^{ [[theValue(0) should] equal:theValue(0)]; }); }); });
18. Kiwi describe(@"Tested class", ^{ context(@"When created", ^{ it(@"should not fail", ^{ id viewController = [ViewController new]; [[viewController should] conformToProtocol:@protocol(UITableViewDelegate)]; }); }); });
19. Matchers [subject  shouldNotBeNil] • [subject  shouldBeNil] • [[subject  should]  beIdenticalTo:(id)anObject] - compares id's • [[subject  should]  equal:(id)anObject] • [[subject  should]  equal:(double)aValue  withDelta: (double)aDelta] • [[subject  should]  beWithin:(id)aDistance  of:(id)aValue] • [[subject  should]  beLessThan:(id)aValue] • etc.  etc.
20. Compare to SenTesting Kit [[subject  should]  equal:anObject] compare  with STAssertEquals(subject,  anObject,  @”Should  be  equal”);
21. OCMock • Mocking and stubbing library for iOS • Quite versatile • Makes use of NSProxy magic
22. Sample workflows
23. Classic calculator sample describe(@"Calculator",  ^{                context(@"with  the  numbers  60  and  5  entered",  ^{                RPNCalculator  *calculator  =  [[RPNCalculator  alloc]  init];                                beforeEach(^{                        [calculator  enter:60];                        [calculator  enter:5];                });                afterEach(^{                          [calculator  clear];                });                              it(@"returns  65  as  the  sum",  ^{                        [[theValue([calculator  add])  should]  equal:65  withDelta:.01];                });
24. Test if calls dep methods 1. Create a mock dependency 2. Inject it 3. Call the method 4. Verify
25. Test dependency // Create the tested object and mock to exchange part of the functionality viewController = [ViewController new]; mockController = [OCMockObject partialMockForObject:viewController]; // Create the mock and change implementation to return our class id serviceMock = [OCMockObject mockForClass:[InterwebzService class]]; [[[mockController stub] andReturn:serviceMock] service]; // Define expectations [[serviceMock expect] downloadTweetsJSONWithSuccessBlock:[OCMArg any]]; // Run the tested method [viewController tweetsButtonTapped:nil]; // Verify - throws exception on failure [mockController verify];
26. Testing one layer • Isolate dependencies • Objective-C is highly dynamic - we can change implementations of private methods or static methods • We can avoid IoC containers for testing
27. Accessing private methods
28. Accessing private methods @interface ViewController() - (void)startDownloadingTweets; @end ... [[mockController expect] startDownloadingTweets];
29. Static method testing • Through separation to a method @interface ViewController() - (NSUserDefaults *)userDefaults; @end ... id mockDefaults = [OCMockObject mockForClass:[NSUserDefaults class]]; [[[mockDefaults expect] andReturn:@"Setting"] valueForKey:[OCMArg any]]; [[[mockController stub] andReturn:mockDefaults] userDefaults];
30. Static method testing • Through method swizzling void  SwizzleClassMethod(Class  c,  SEL  orig,  SEL  new)  {        Method  origMethod  =  class_getClassMethod(c,  orig);        Method  newMethod  =  class_getClassMethod(c,  new);        c  =  object_getClass((id)c);        if(class_addMethod(c,  orig,  method_getImplementation(newMethod),  method_getTypeEncoding(newMethod)))                class_replaceMethod(c,  new,  method_getImplementation(origMethod),   method_getTypeEncoding(origMethod));        else                method_exchangeImplementations(origMethod,  newMethod); }
31. Normal conditions apply despite it’s iOS & Objective--C
32. Problems of „mobile devs” • Pushing code with failing tests • Lot’s of hacking together • Weak knowledge of VCS tools - merge nightmares
33. Ending thoughts • Think first (twice), then code :) • Tests should come first • Write the failing test, pass the test, refactor • Adequate tools can enhance your testing experience
34. Ending thoughts • Practice!
35. Thanks!
36. Questions