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The Road To Test-Driven Development

The Road To Test-Driven Development By Christopher Paulicka Software Engineering Manager Introduction Not just what Test-Driven Development is… But also how to get to Test-Driven Development Agenda What is Test-Driven Development One (Abstract) Road to Test-Driven Development

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The Road To Test-Driven Development

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  1. The Road To Test-Driven Development By Christopher Paulicka Software Engineering Manager Copyright Oversee.net 2008

  2. Introduction • Not just what Test-Driven Development is… • But also how to get to Test-Driven Development Copyright Oversee.net 2008

  3. Agenda • What is Test-Driven Development • One (Abstract) Road to Test-Driven Development • Your Road to Test-Driven Development • My Road to Test-Driven Development Copyright Oversee.net 2008

  4. Vocabulary • Test-Driven Development – TDD • Extreme Programming - XP Copyright Oversee.net 2008

  5. Thanks • Perl Mongers for showing up! • Oversee.net for the nice space • Michael Lee, Director of Engineering, for “volunteering” me • All the development team here at Oversee for feedback Copyright Oversee.net 2008

  6. The Three Participants • Christopher Paulicka • Oversee.net • Perl Mongers Copyright Oversee.net 2008

  7. Christopher Paulicka • Software Development – 16 years • Testing – 10 years • Perl – 4 years • Test-Driven Development – 1 year Copyright Oversee.net 2008

  8. Oversee Development Environment • Agile/Scrum • Perforce • Linux/Apache/MySQL/Perl, RPM • Mason/Catalyst, DBI • Test::More, Test::MockObject • Test::Unit, Test::WWW::Selenium • Module::Build, CPAN2RPM Copyright Oversee.net 2008

  9. Perl Mongers • Perl aficionados • Please ask questions at any time • What’s your testing experience? Copyright Oversee.net 2008

  10. What is TDD • TDD is old, but kind of new • Test first, but still follow requirements • Part of Agile/XP, but reusable anywhere Copyright Oversee.net 2008

  11. Important to Know • History of TDD in Extreme Programming • History of Scrum at Oversee Copyright Oversee.net 2008

  12. Software Development Methodologies • Hack • Waterfall • Agile Copyright Oversee.net 2008

  13. Waterfall Development • Requirements • Design • Implement • Test • Maintain Copyright Oversee.net 2008

  14. Waterfall Costs • Rigid design • High change costs • Requires expert designers up front Copyright Oversee.net 2008

  15. Examples of Agile Methodologies • Extreme Programming • Scrum • Crystal Clear • Feature Driven Development • Adaptive Software Development • DSDM Copyright Oversee.net 2008

  16. Extreme Programming • Test-Driven Development • Continuous Integration • Pair Programming • Refactoring Copyright Oversee.net 2008

  17. Cost of Feedback Copyright Oversee.net 2008

  18. Test-Driven Development • Pick a Feature • Write a Test for that Feature • Run all Tests and see new Test Fail • Write Code for Feature • Run all Tests and see all Tests Pass • Refactor • Repeat Copyright Oversee.net 2008

  19. A Bit More About Refactoring • Refactor the Code • Refactor the Tests • Refactor the Documentation • Refactor the Design Copyright Oversee.net 2008

  20. Who owns testing? • QA • Deploy • Systems • Development Copyright Oversee.net 2008

  21. Types of Testing • Requirements Tests • Integration Tests • System Tests • Development Tests Copyright Oversee.net 2008

  22. Types of Development Testing • Unit Tests • Regression Tests Copyright Oversee.net 2008

  23. One Possible Road to TDD • Test to Verify • Test for Regression • Test for Design • Test-Driven Development Copyright Oversee.net 2008

  24. Test To Verify • Problem arises • Write throw away test • Disposable code modifications • Logging • Dumping, etc • Simple and Fast • Gone forever… Copyright Oversee.net 2008

  25. Why Do We Do That? • Habit • Speed • Anticipation (almost done…) Copyright Oversee.net 2008

  26. Test for Regression • Problem arises • Write reusable test that duplicates problem • Keep regression test • Run regressions anytime Copyright Oversee.net 2008

  27. Good, but Good enough? • Bug driven • Prevents regressions • Run tests anytime in development • Focused late in the curve • Expects test framework Copyright Oversee.net 2008

  28. Test for Design • Design API • Write Code • Write Tests • Refactor Copyright Oversee.net 2008

  29. Development Test Processes • Piece-wise Test Last • Lump-sum Test Last • Test First aka TDD Copyright Oversee.net 2008

  30. Test-Driven Development • As Beck said in XP • Good Rules, lead to • Good Behavior, which give • Good Unit Tests Copyright Oversee.net 2008

  31. Rules • Write code only when test fails • Eliminate duplication afterwards Copyright Oversee.net 2008

  32. Behaviors • Organic Design • Writing own tests • Rapid response • Modular Design Copyright Oversee.net 2008

  33. Good Unit Tests • Run fast • Run in isolation • Easy to understand • Use real data • Incremental step (not too large) Copyright Oversee.net 2008

  34. Your Road To TDD • Why TDD • Cost/Benefit Analysis • How To Start Copyright Oversee.net 2008

  35. Why Test Driven Design • Tests as Use Cases • Tests as Documentation • Tests as Design Copyright Oversee.net 2008

  36. Possible reasons to avoid TDD • Tests are programmer focused • May not be requirement focused • Running all tests are slow • Sprinting • Refactoring • Comparing Copyright Oversee.net 2008

  37. Cost/Benefit of TDD • Industry Analysis • Personal Analysis Copyright Oversee.net 2008

  38. Benefits - Industry Analysis • Reduce development lead-time significantly • Programmers that write tests are more productive • Rarely use a debugger • Easy to revert on test failure • … Copyright Oversee.net 2008

  39. Benefits – Industry Analysis (cont) • Programmers tests interface first, then code • Shorter implementation time • High Code coverage • Regressions • More modular code Copyright Oversee.net 2008

  40. Costs – Industry Analysis • More code • Though higher productivity with TDD • Costly test setup • UI • DB • Multithreaded • Large legacy code bases Copyright Oversee.net 2008

  41. Metrics – Industry Analysis • TDD code passed 18 - 50% more external test cases than control group code • TDD code had 10 – 50% less time spent debugging code • TDD had from 0 - 16% decrease in productivity (in lines of non-test code) • … Copyright Oversee.net 2008

  42. Metrics – Industry Analysis (cont) • TDD has 163% more asserts/module • TDD 2-3x higher test coverage • line and condition coverage near 100% • TDD coders spent 13% less time producing solutions that were 12% larger then control (including tests!) Copyright Oversee.net 2008

  43. Subjective – Industry Analysis After the study, when asked: • TDD would stick with TDD • TLD would go to TDD (60%+) • No tests would go to TLD Copyright Oversee.net 2008

  44. Benefits – Personal Analysis • Senior/Junior Developer Interaction • Senior approve tests/API • Junior implements API • Senior code reviews, done • Tests as Use Cases • Test Documentation more stable then Code Documentation Copyright Oversee.net 2008

  45. Costs – Personal Analysis • More code • Though happier with more feedback • Costly test setup • UI - WWW::Mechanize • DB – Test::MockObject • Multithreaded - …heh…yes. • Large Legacy Codebases are painful, but TDD may be very beneficial…it’s a start! Copyright Oversee.net 2008

  46. How To Start • Believe in Testing • Test Framework • Test Coverage • Write Tests First Copyright Oversee.net 2008

  47. Believe in Testing • If it's worth building, it's worth testing. • If it's not worth testing, why are you wasting your time working on it? Copyright Oversee.net 2008

  48. Test Frameworks Perl has a lot… • Test::Simple • Test::More • Test::Unit Copyright Oversee.net 2008

  49. Test Coverage • Provide metrics • Devel::Cover Copyright Oversee.net 2008

  50. Write Tests First • Code review tests • Pair program tests • Always ask, “Where’s the test?” • Help make tests easier Copyright Oversee.net 2008

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