Testing in iOS 10.01.2013 by Tomasz Janeczko 

About me Tomasz Janeczko • iOS developer in Kainos • Enthusiast of business, electronics, Rails & Heroku • Organizer of first App Camp in UK and PL 

So let’s talk about testing. 

Why we test? 

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So? 

• Reliability • Regression • Confidence (e.g. refactoring) 

Why not to test? 

Why not to test? • Heavy dependence on UI • Non-testable code • Bad framework 

How to address issues • Sample - downloading stuff from interwebz 

First fault Writing tests after writing code 

Separation of concerns 

Separation of concerns • Let’s separate out the UI code • Same for services interaction 

Demo of tests 

Writing tests Meet Kiwi and OCMock 

Kiwi • RSpec-like tests writing • Matchers • Cleaner and more self-descriptive code 

Kiwi describe(@"Tested class", ^{ context(@"When created", ^{ it(@"should not fail", ^{ [[theValue(0) should] equal:theValue(0)]; }); }); }); 

Kiwi describe(@"Tested class", ^{ context(@"When created", ^{ it(@"should not fail", ^{ id viewController = [ViewController new]; [[viewController should] conformToProtocol:@protocol(UITableViewDelegate)]; }); }); }); 

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. 

Compare to SenTesting Kit [[subject  should]  equal:anObject] compare  with STAssertEquals(subject,  anObject,  @”Should  be  equal”); 

OCMock • Mocking and stubbing library for iOS • Quite versatile • Makes use of NSProxy magic 

Sample workflows 

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];                }); 

Test if calls dep methods 1. Create a mock dependency 2. Inject it 3. Call the method 4. Verify 

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]; 

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 

Accessing private methods 

Accessing private methods @interface ViewController() - (void)startDownloadingTweets; @end ... [[mockController expect] startDownloadingTweets]; 

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]; 

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); } 

Normal conditions apply despite it’s iOS & Objective--C 

Problems of „mobile devs” • Pushing code with failing tests • Lot’s of hacking together • Weak knowledge of VCS tools - merge nightmares 

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 

Ending thoughts • Practice! 

Thanks! 

Questions