The Road to Test Driven Development

04/10/23Copyright Oversee.net 20081

The Road To Test-Driven The Road To Test-Driven DevelopmentDevelopment

By Christopher PaulickaSoftware Engineering Manager

Introduction Introduction

Not just what Test-Driven Development is…

But also how to get to Test-Driven Development

AgendaAgenda

What is Test-Driven DevelopmentOne (Abstract) Road to Test-Driven

DevelopmentYour Road to Test-Driven DevelopmentMy Road to Test-Driven Development

VocabularyVocabulary

Test-Driven Development – TDDExtreme Programming - XP

ThanksThanks

Perl Mongers for showing up!Oversee.net for the nice spaceMichael Lee, Director of Engineering, for

“volunteering” meAll the development team here at Oversee

for feedback

The Three ParticipantsThe Three Participants

Christopher PaulickaOversee.netPerl Mongers

Christopher PaulickaChristopher Paulicka

Software Development – 16 yearsTesting – 10 yearsPerl – 4 yearsTest-Driven Development – 1 year

Oversee Development Oversee Development EnvironmentEnvironmentAgile/ScrumPerforceLinux/Apache/MySQL/Perl, RPMMason/Catalyst, DBITest::More, Test::MockObjectTest::Unit, Test::WWW::SeleniumModule::Build, CPAN2RPM

Perl MongersPerl Mongers

Perl aficionadosPlease ask questions at any timeWhat’s your testing experience?

What is TDDWhat is TDD

TDD is old, but kind of newTest first, but still follow requirementsPart of Agile/XP, but reusable anywhere

Important to KnowImportant to Know

History of TDD in Extreme ProgrammingHistory of Scrum at Oversee

Software Development Software Development MethodologiesMethodologiesHackWaterfallAgile

Waterfall DevelopmentWaterfall Development

RequirementsDesignImplementTestMaintain

Waterfall CostsWaterfall Costs

Rigid designHigh change costsRequires expert designers up front

Examples of Agile Examples of Agile MethodologiesMethodologiesExtreme ProgrammingScrumCrystal ClearFeature Driven DevelopmentAdaptive Software DevelopmentDSDM

Extreme ProgrammingExtreme Programming

Test-Driven DevelopmentContinuous IntegrationPair ProgrammingRefactoring

Cost of FeedbackCost of Feedback

Test-Driven DevelopmentTest-Driven Development

Pick a FeatureWrite a Test for that FeatureRun all Tests and see new Test FailWrite Code for FeatureRun all Tests and see all Tests PassRefactorRepeat

A Bit More About RefactoringA Bit More About Refactoring

Refactor the CodeRefactor the TestsRefactor the DocumentationRefactor the Design

Who owns testing?Who owns testing?

QADeploySystemsDevelopment

Types of TestingTypes of Testing

Requirements TestsIntegration TestsSystem TestsDevelopment Tests

Types of Development TestingTypes of Development Testing

Unit TestsRegression Tests

One Possible Road to TDDOne Possible Road to TDD

Test to VerifyTest for RegressionTest for DesignTest-Driven Development

Test To VerifyTest To Verify

Problem arisesWrite throw away testDisposable code modifications

– Logging– Dumping, etc

Simple and FastGone forever…

Why Do We Do That?Why Do We Do That?

HabitSpeedAnticipation (almost done…)

Test for RegressionTest for Regression

Problem arisesWrite reusable test that duplicates problemKeep regression testRun regressions anytime

Good, but Good enough?Good, but Good enough?

Bug driven Prevents regressionsRun tests anytime in developmentFocused late in the curveExpects test framework

Test for DesignTest for Design

Design APIWrite CodeWrite TestsRefactor

Development Test ProcessesDevelopment Test Processes

Piece-wise Test LastLump-sum Test LastTest First aka TDD

Test-Driven DevelopmentTest-Driven Development

As Beck said in XP– Good Rules, lead to – Good Behavior, which give– Good Unit Tests

RulesRules

Write code only when test failsEliminate duplication afterwards

BehaviorsBehaviors

Organic DesignWriting own testsRapid responseModular Design

Good Unit TestsGood Unit Tests

Run fastRun in isolationEasy to understandUse real dataIncremental step (not too large)

Your Road To TDDYour Road To TDD

Why TDDCost/Benefit AnalysisHow To Start

Why Test Driven DesignWhy Test Driven Design

Tests as Use CasesTests as DocumentationTests as Design

Possible reasons to avoid TDDPossible reasons to avoid TDD

Tests are programmer focusedMay not be requirement focusedRunning all tests are slowSprintingRefactoringComparing

Cost/Benefit of TDDCost/Benefit of TDD

Industry AnalysisPersonal Analysis

Benefits - Industry AnalysisBenefits - Industry Analysis

Reduce development lead-time significantly

Programmers that write tests are more productive

Rarely use a debuggerEasy to revert on test failure…

Benefits – Industry Analysis (cont)Benefits – Industry Analysis (cont)

Programmers tests interface first, then code

Shorter implementation timeHigh Code coverageRegressionsMore modular code

Costs – Industry AnalysisCosts – Industry Analysis

More code– Though higher productivity with TDD

Costly test setup– UI– DB– Multithreaded

Large legacy code bases

Metrics – Industry AnalysisMetrics – 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)

Metrics – Industry Analysis (cont)Metrics – Industry Analysis (cont)

TDD has 163% more asserts/moduleTDD 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!)

Subjective – Industry AnalysisSubjective – Industry Analysis

After the study, when asked:TDD would stick with TDDTLD would go to TDD (60%+)No tests would go to TLD

Benefits – Personal AnalysisBenefits – Personal Analysis

Senior/Junior Developer Interaction– Senior approve tests/API– Junior implements API– Senior code reviews, done

Tests as Use CasesTest Documentation more stable then

Code Documentation

Costs – Personal AnalysisCosts – 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!

How To StartHow To Start

Believe in TestingTest FrameworkTest CoverageWrite Tests First

Believe in TestingBelieve 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?

Test FrameworksTest Frameworks

Perl has a lot…Test::SimpleTest::MoreTest::Unit

Test CoverageTest Coverage

Provide metricsDevel::Cover

Write Tests FirstWrite Tests First

Code review testsPair program testsAlways ask, “Where’s the test?”Help make tests easier

Be Aware!Be Aware!

You are now becoming a test expert!TDD AntipatternsDon’t test just to test…

My Road To Test-Driven My Road To Test-Driven DevelopmentDevelopmentHewlett-Packard EMSOIdealab

– X1– Energy Innovations

Lessons from Hewlett-PackardLessons from Hewlett-Packard

Tests are nowhere near perfectTests can prove your pointBelieve in tests!

Tests are nowhere near perfectTests are nowhere near perfect

500000 lines of codeHundreds of feature tests workingApplications run for 3 daysI knew it was broken

Tests can prove your pointTests can prove your point

No one wanted to believe itThe product needed to shipWrote random component

creator/messenger/destroyerCore dump in less then a millisecondCreated tests from random iterationsFixed hundreds of memory leaks and

contention issues

Lessons from X1Lessons from X1

Good Test FrameworkKeep each other honest

Good Test FrameworkGood Test Framework

Test::UnitWWW::MechanizeDBI

– No MockObjects

Keep each other honestKeep each other honest

Test First, not test eventuallyEverybody Writes Tests……but feel free to ask for help

Lessons from Energy Lessons from Energy InnovationsInnovationsCost of RefactoringBeware Gold PlatingIt’s easy to get lazy…

SummarySummary

Learned about TDDLearned about benefits (and costs) of TDDLearned first steps towards TDD

Q&AQ&A

BibliographyBibliography I would highly recommend “The Object Primer”

by Scott W. Ambler, now in it’s third edition. http://www.agiledata.org/essays/tdd.html http://en.wikipedia.org/wiki/Test-driven_develop

ment http://en.wikipedia.org/wiki/Agile_software_dev

elopment http://en.wikipedia.org/wiki/Continuous_integrat

ion http://en.wikipedia.org/wiki/Refactoring …

Bibliography (cont)Bibliography (cont)

http://blog.james-carr.org/?p=44http://www.ipd.uka.de/Tichy/uploads/publi

kationen/136/MuellerHoefer2007.pdfhttp://www.acm.org/src/subpages/gf_entri

es_06/DavidJanzen_src_gf06.pdfhttp://utopia.csis.pace.edu/dps/2008/mcape

llan/projects/TDD/TDD_Idea_Paper_V04-03.doc

Bibliography (cont)Bibliography (cont)

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B75H1-4FC40MJ-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=fbd92b394263506930dfafb31003a916

http://aegis.sourceforge.net/

The Road to Test Driven Development

tdd tests

tdd tdd

test driven design tests

db test

reusable test

design testdriven development

dbi test

mockobject test

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