Introductory talk about Unit Testing for iOS: Motivations and basics. Some example code included.

1. 7 Stages of Unit
Testing in iOS
Jorge D. Ortiz-Fuentes
@jdortiz
#7SUnitTest

2. A Canonical
Examples
production
#7SUnitTest

3. #7SUnitTest
Agenda
Evangelize about unit tests to seasoned
programmers
Introduce them to everybody else

4. 1.

5. Shock & Disbelief

6. But my code is
always awesome!

7. #7SUnitTest
Unit Tests
Prove correctness of different aspects of the
public interface.
• Prove instead of intuition
• Define contract and assumptions
• Document the code
• Easier refactoring or change
Reusable code = code + tests

8. Test the parts
that you aren’t
developing now

9. #7SUnitTest
Use Unit Testing
Incrementally
You don’t have to write every unit test
Start with the classes that take care of the
logic
• If mixed apply SOLID
The easier entry point are bugs

10. 2.

11. Denial

12. C’mon, it takes
ages to write
tests!

13. Time writing tests <
Time debugging

14. #7SUnitTest
Good & Bad News
Most already available in Xcode / not doubles
Projects are created with
• test target
• a crappy example
⌘+U is your friend
Behaviors provide Pavlov reinforcement
XCTest is THE tool for the rest you are on your own

15. 3.

16. Anger

17. How do I write
those f***ing
tests?

18. #7SUnitTest
Types of Unit Tests
Test return value
Test state
Test behavior

19. #7SUnitTest
The SUT
@interface Thermostat : NSObject
@property (strong, nonatomic) NSNumber *setpoint;
@property (assign, nonatomic) BOOL imperialSystem;
- (NSString *) showSetpoint;
- (void) increaseSetpoint;
- (void) saveSetpoint;
@end

20. #7SUnitTest
Return
- (NSString *) showSetpoint {
return [NSString stringWithFormat:@"%@ %@", self.setpoint,
self.imperialSystem?@"F":@"C"];
}

21. #7SUnitTest
Test return
- (void) testSetpointIsShownWithTheRightUnits {
// Arrange
sut.setpoint = @23;
sut.imperialSystem = NO;
// Act
NSString *shownSetpoint = [sut showSetpoint];
// Assert
XCTAssertEqualObjects(shownSetpoint, @"23 C");
}

22. #7SUnitTest
State
- (void) increaseSetpoint {
self.setpoint = @([self.setpoint intValue] + 1);
}

23. #7SUnitTest
Test state
- (void) testIncreaseSetpointAddsOne {
// Arrange
sut.setpoint = @23;
// Act
[sut increaseSetpoint];
// Assert
XCTAssertEqualObjects(sut.setpoint, @24);
}

24. #7SUnitTest
Behavior
@interface Thermostat()
@property (strong, nonatomic) NSUserDefaults *userDefaults;
@end
@implementation Thermostat
- (void) saveSetpoint {
[self.userDefaults setObject:self.setpoint
forKey:@"setpoint"];
}
- (NSUserDefaults *) userDefaults {
if (_userDefaults == nil) {
_userDefaults = [NSUserDefaults standardUserDefaults];
}
return _userDefaults;
}
@end

25. #7SUnitTest
Create a Spy
@interface UserDefaultsMock: NSUserDefaults
@property (assign, nonatomic) BOOL valueWasSet;
@end
@implementation UserDefaultsMock
- (void)setValue:(id)value forKey:(NSString *)key {
self.valueWasSet = YES;
}
@end

26. #7SUnitTest
Test behavior
- (void) testSetpointIsPersisted {
// Arrange
sut.setpoint = @23;
UserDefaultsMock *userDefMock = [UserDefaultsMock new];
[sut setValue:userDefMock forKey:@"userDefaults"];
// Act
[sut saveSetpoint];
// Assert
XCTAssertTrue(userDefMock.valueWasSet);
}

27. 4.

28. Bargain

29. Ok, I’ll write
some tests, but
make my life
simpler

30. - (void) testSetpointIsPersisted {
// Arrange
sut.setpoint = @23;
id userDefMock = [OCMockObject mockForClass:[NSUserDefaults class]];
OCMExpect([userDefMock setObject:sut.setpoint forKey:@"setpoint"]);
[sut setValue:userDefMock forKey:@"userDefaults"];
// Act
[sut saveSetpoint];
// Assert
XCTAssertNoThrow([userDefMock verify]);
}
Simulating and Testing
Behavior
Stubs & Mocks
• Both are test doubles
• Stubs provide desired responses to the SUT
• Spies also expect certain behaviors
• Mocks include verification

31. #7SUnitTest
Use a Mocking
Framework
Install as a pod
• OCMock
• OCMockito
Not for Swift 😱

32. #7SUnitTest
Dependency Injection
Control behavior of the dependencies
• Constructor
• Method overwriting
• Property injection:Lazy instantiation
Or use a DI framework (uncommon)

33. #7SUnitTest
An Assertion Framework
Richer semantics
• OCHamcrest
• Expecta
• Nimble

34. 5.

35. Guilt

36. My tests are
never good
enough!

37. #7SUnitTest
Follow the rules
Test your code only
Only a level of abstraction
Only public methods
Only one assertion per test
Tests are independent of sequence or state

38. 6.

39. Depression

40. But my coverage
is poor

41. #7SUnitTest
Improve your coverage
Measure it
Assign priorities
Agree upon rules for your team/project

42. Coverage

43. Improve

44. #7SUnitTest
And when I have too
many tests?
Disable test cases
Run from command line
• xcodebuild
• xcpretty

45. 7.

46. Acceptance &
Hope

47. No tests, no fun

48. #7SUnitTest
Evolve
Clean Architecture
TDD
Other tests: integration, ui, performance…
CI (OSX Server / Jenkins)

49. Thank
you!

50. @jdortiz
#7SUnitTest