smb:zambeellearningtdd

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smb//zambeel/learning/tdd
smb//192.168.0.5/learning/tdd

• Demo project for this presentation,
  MyTemperatureCalculator.zip also available at the
  above link

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iPhone Unit Testing with Google Toolbox for Mac
(GTM)

• Muhammad Ishaq
• Software Engineer, Tintash (Pvt) Ltd
• 01/15/2009

NOTE This presentation is based on the OCUnit
article at http//developer.apple.com/tools/unitt
est.html
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Google Toolbox for Mac (GTM)

• From GTM Homepage
• A collection of source from different Google
  projects that may be of use to developers working
  other Mac projects. Also includes the Google
  Developer Spotlight Importers.
• Whats in it for Us?
• Unit testing for the iPhone at least
• may be a lot more (note to self Explore)

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Lets get to business

• Download and extract google-toolbox-for-mac (GTM)
  from http//code.google.com/p/google-toolbox-for-
  mac/downloads/list
• In your Xcode project
• create a new target to run the unit tests, lets
  call it RunAllTests
• from google-toolbox-for-mac/UnitTesting/, add
  these to RunAllTests target
• GTMIPhoneUnitTestMain.m
• GTMSenTestCase.h/GTMSenTestCase.m
• GTMIPhoneUnitTestDelegate.h/GTMIPhoneUnitTestDeleg
  ate.m
• you also need to add google-toolbox-for-mac/GTMDef
  ines.h
• add a new Run Script Build Phase to the end of
  target phases
• shell should be set to /bin/sh
• and the script to google-toolbox-for-mac/UnitTest
  ing/RunIPhoneUnitTest.sh
• thats it, build the target, if you hit Build and
  Go, Unit Tests would be executed twice (once for
  Build and once for Run)

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GTM Is Configured, Lets Code

• So heres the problem statement

design a class that - can convert from
Centigrade to Kelvin

• We are doing TDD, so lets write a test for the
  requirement

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Create a TestCase Class

• Add a new class to the target via File New File
  and choose "Objective-C test case class" from the
  Mac OS X Cocoa group
• Call it TestTempratureCalculator1

• 1 We plan to call our class TemperatureCalculato
  r, the test case class by convention should be
  called TestTempratureCalculator

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Initial .h file
NOTE the lines I modified are highlighted in
yellow
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Initial .m file
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Lets add our first Test Case

• converting 0C to Kelvin should return 273K, unit
  test declaration is highlighted below

NOTE the lines I modified are highlighted in
yellow
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and here is the implementation
NOTE the lines I modified are highlighted in
yellow
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Build the RunAllTests target

• ofcourse, we need to add TemperatureCalculator
  with a convertFromCentigrade method defined for
  the target to compile

• but since we are writing code essentially to pass
  the test, well make convertFromCentigrade to
  return hardcoded 273, its enough to pass our
  tests (for now).

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Add the missing code

• Adding the missing code makes the test pass

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How about another test?

• okay, our TemperatureCalculature can successfully
  convert freezing point to Kelvins (or so it
  seems), how about boiling point?
• add a new test case called testBoilingPointConvers
  ion that should check that converting 100C
  should return 373K, it should be declared like
  this

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and the implementation is

• now if we try to build the RunAllTests target, it
  fails

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update the code

• the failing test complains that
  TemperatureCalculator returned 273 instead of 373
  (the expected value), turns out return hard-coded
  273 was not a good idea after all. Lets update it

our tests pass now, but!
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Our tests have redundant code
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Fixtures

• In generic xUnit, a test fixture is all the
  things that must be in place in order to run a
  test and expect a particular outcome. (from
  wikipedia)
• we typically have
• setUp selector to do any initialization for a
  test
• tearDown selector to do the cleanup
• NOTE Fixtures are not constructors/destructors,
  each test case gets its own copy of them (in
  contrast to same constructor/destructor being run
  for all methods of a class) to say the least.

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Fixtures, lets apply

• So, lets extract the duplicate code to setUp and
  tearDown selectors
• both of our test cases require a
  TemperatureCalculator instance, so we can make it
  a member variable
• the header file is now

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Fixtures, implementation
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New Feature

• so far so good, but heres a new feature

• calculate the boiling point of water in a given
  city based on barometric pressure

Formula for calculation is
Boiling Point of Water 49.161 Ln(Barometric
Pressure) 44.932
NOTE Formula returns boiling point in Fahrenheit
scale, for simplicity, I am not going to convert
it to Kelvin
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Yet another test

• so if the barometric pressure in Denver, Colorado
  is currently 24.896 inches of Mercury, then the
  boiling point of water is approximately 202
  degrees Fahrenheit

• lets write a test

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How to implement the feature?

• Okay, so may be we can code boilingPointOfWaterInC
  ity such that it looks up the barometric
  pressures from AccuWeather.com over the internet,
  right?

• Almost!

• We can implement it like that but in that case
  our test case would only pass if the current
  barometric pressure in Denver is exactly 24.896
  inches of Mercury

• Hmm

• We should probably decouple weather lookup
  service from our TemperatureCalculator

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Design Feedback from TDD

• So, may be we can make a protocol called
  WeatherLookupService, and we make our test case
  class conform to this protocol. The
  implementation, however, returns values
  appropriate for our test cases?

• Sound like a plan?

• Heres an informal WeatherLookupService protocol

NOTE WeatherLookupService protocol is defined in
TemperatureCalculator.h
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TemperatureCalculator updated

• heres the updated header file

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TemperatureCalculator updated

• corresponding implementation is

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Test case needs an update too!

• Our test case class (in this case) acts as a Mock
  object by the way.

• A Mock object is an object that mimics the
  behavior of a real object to simplify testing

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Thats it!

• Build the RunAllTests target, all tests should
  pass

• Heres what we covered today
• Configuring Google Toolbox for Mac (GTM)
• Write simple unit tests
• Use Fixtures
• Using Mock Objects to simplify testing

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Fruit for Thought

• Heres what we did not cover
• GTM Log Tracking
• GTM UI Unit Testing
• GTM HTTP Unit Testing
• GTM Code Coverage Analysis
• GTMDebugSelectorValidation
• GTMMethodCheck

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Notes

• Unit Tests cannot be run while iPhone Simulator
  is running, if you do, you may receive an error
  like this
• Couldn't register PurpleSystemEventPort with the
  bootstrap server. Error unknown error code. This
  generally means that another instance of this
  process was already running or is hung in the
  debugger.
• GTM has several assert macros, find them inside
  google-toolbox-for-mac/UnitTesting/GTMSenTestCase.
  h
• GTM does not support binding unit testing on the
  iPhone as NSBinding is not supported on the
  iPhone.

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Resources

• GTM http//code.google.com/p/google-toolbox-for-m
  ac/ (make sure to check out the wiki pages as
  well)
• Unit Testing with OCUnit http//developer.apple.c
  om/tools/unittest.html
• TDD for Games http//gamesfromwithin.com/?p50
• Jeff on Games http//www.jeffongames.com/categoy/
  programming/unit-testing/
• Book Beck, Kent, Test Driven Development By
  Example. Addison-Wesley, 2002

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Questions?

• NOTE Zambeel Resource Folder smb//zambeel/learn
  ing/tdd/