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TDR&TDDTest-Driven{Requirements&Development}ByMikeRieser (email:mike@mrieser.com)

ENGINEERING PRACTICES

“PeoplehavetoldmethattheyseeScrumasthemanagementapproachtoagiledevelopmentandXPastheengineeringpracticesthatmakeiteffective,bothbondedtogetherbycomplimentarypracticesandgoals.”

– KenSchwaber

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ScrumforProcess, ExtremeProgramming(XP)forPractices

“Accordingly,wheneverIhaveasituationinwhichsoftwareisbeingdeveloped,Scrumisbeingused,andtheengineeringpracticesaresubstandard,IalsocallforXPtobeimplemented.”

– KenSchwaber

#3

Scrum’s InfluenceonExtremeProgramming(XP)

From: Kent Beck To: Jeff Sutherland <jsutherland>

Reply: 70761.1216@compuserve.com

Date: Mon, 15 May 1995 18:01:15 -0400 (EDT)

Subj: HBR paper

_____________________________________________________Isthere agoodplace togetreprints ofthe SCRUM paper fromHBR? I'vewritten patterns for something verysimilar andIwanttomakesure Istealasmanyideas aspossible.

Kent

#4

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MATURINGPRACTICES

DiscussionTeamsnewtoScrumtypically startbyputtingeverythinginprogressandtreatingtheiterationlikeamini-waterfall.

Howhaveyouseenteamsmature inthewaytheyapproachandaccomplish theirwork?

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SkillMaturityModelsAgile teamsmatureintheir skillsandpractices:• DreyfusModel: Novice toExpert.• MartialArts: Shu-Ha-Ri.• Meilir Page-Jones: InnocenttoResearcher.

NoviceAgileTreat anIteration likeamini-waterfall. Allstories putin flight atonce.QAgetssqueezed atthe

endhaving totesteverything thenight before the demo.

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QAPlightTheTester isattheendoftheprocessandmayhavequestions.

?

?

AdvancedBeginnerTeamstarts completing stories earlier, butstill approaches eachstory inatraditional fashion.

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StevenCoveytip: “Beginwith theendinmind.”Let’sisolateaUser Storyandthinkaboutit.

“Beginwiththeendinmind.”WhatifwebeganwithQATesting?

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QATestsandRequirements atthestart.Thiswrapsalotofthingsaround.NoticewheretheBAandQA endup?

Separate outtheDevtasks.

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Isolateeacharea.

Rearrange theDevtasks. Codemovesearlier.

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We’llredirect theflow.

AnalysisfeedsTests.FromTestswegostraight toCode.

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Let’snameeachofthesekeyareas.

Test-DrivenRequirements +Test-DrivenDevelopment

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Mature teamwithmature practicesPracticingTest-DrivenRequirementswithTest-DrivenDevelopment

TEST-DRIVENREQUIREMENTS

“Anexamplewouldbehandyrightaboutnow.”– BrianMarick

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TestTablesarebestdonecollaboratively!

SoftwareRequirements asaTable“...anysoftwareprogramcanbethoughtofasatablethatmapsprograminputstotheircorrespondingcorrectoutputs.Thischaracterizationofprogrammingassumesafinitenumberoffiniteinputs,whichisfairforpracticalpurposes” 27

July 2001 issue of ACM Software Engineering Notes, J. P. Lewis

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WorldofWarcraftCharacterMovementCharacter MovementCharacterName

CharacterLocation

ObjectLocation Move Location? #Comment

Operandi (0, 0,0) - Forward (1,0,0) Unhinderedmovement

Operandi (0,0, 0) (-1, 0,0) Backward (0,0,0) Blockedmovement

Persona!

ATMWithdrawCashTestTableWithdraw Cash

ATM CashAccountBalance

RequestAmount Result?

ATMCash?

AccountBalance? #Comment

$1,000 $5,000 $100 OK $900 $4,900 Happy

$1,000 $1,000 $1,000 OK 0 0 Boundary

$100 $5,000 $200 ERROR $100 $5,000 InsufficientATMcash

$1,000 $100 $200 ERROR $1,000 $100 Insufficientacct balance

$1,000 -$100 $200 ERROR $1,000 -$135 Overdraftfee!

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Gherkin– Given-When-ThenGiven anAccountwitha$5,000balanceAnd theATMwith$1,000cash

When thePatronwithdraws$100cash

Then theAccountbalance is$4,900And theATMhas$900cash

CommonTools• Fit(orSlim)andFitNesse (JavaorC#)• SpecFlow (C#)• Jbehave (Java)• Cucumber (Ruby)• Concordian• Nominations?

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Discussion• AnyonehavestoriesofTest-DrivenRequirementssparkingcollaboration onteams?

• When’sthebesttimetohavetheteamcreatethetests?

TEST-DRIVENDEVELOPMENT

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SoftwareDevelopment ProcessDependencies

34

Waterfall

UpfrontRequirements

Upfront Design

Agile

Evolutionary Design

Refactoring

Automated DeveloperTests

TestFirst

TestAfter

Test-AfterApproach

TraditionalWay– TestAfter• 1daytothinkanddesign• 2daystowritethecode• Ohyeah,2daystowritetheunittests

DesignJ

CodeK

UnitTestL

35

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Test-FirstApproach

TDDWay– TestFirst• Takesaboutthesametimeasjustdesignandcodedidbefore• UnitTestsseemingly forfree– how?

Writeatest

KMakeitpass

JMakeitright

J

36

WhatisTDD?• DeveloperPractice• Test-FirstProgramming• IncrementalDesign• One testatatime• TDDdoesunittestingbutunittestingisnotnecessarilyTDD

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WhatTDDisNot!• Writing allthetests beforethecode• NotQATesting• Not IntegrationTesting

WhatisRed?Afailing testislikeahuntinglicense tochangeproductioncode.• Enhancements – addatesttoaddnewfunctionality.

• Defects – reproduce thebugasafailingtest.

Onlyintroduceasmuchofatestasyoucangettogreen insay,5mins.

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WhatisGreen?GettoGreenquickly!ObviousImplementation – ifyouknowwhattodo,justdoit!Fake It!– whenyoudon’tuseaconstant!

WhatisRefactor?• Workincrementally.• BeabletoshowGreen aftereachchange.• Removeduplication.• CleanasyouGo!

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Refactor– whatdoyoumean?if ( ... ) {

...i = i + 1;

} else {...i = i + 1;

}

if ( … ) {…

} else {…

}

i = i + 1;

if ( ... ) {...

} else {...

}

i = i + 1;

WhatisIntegrate??• Integrateasfrequentlyaspossible.• Maynotbecomplete,butifdone-enough,shareit.• (ItypicallyavoidcheckinginFakes.)

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Test-Firstvs Test-AfterTest-First

• Thetestsgetwritten.• Testablecodeisgenerallyflexiblecode.

• Lowercoupling• Highercohesion• AllowsRefactoring• Confidence

Test-After

• Sometimestheunittestsget“skipped.”

• Teststhatstartfromawizardaregenerallyprettypoor.

WhatAreUnitTests?• Testswhichhaveaspecific focuswhichcallamethod(orfunction).

• Verify thatthe requirements arebeingmetbythecodewhentestedinisolation.

• “Likeacompiler” forthebusiness requirements.

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WhatUnitTestsareNOT!

BenefitsofTDD?• Testfirstismorefunthattestafter• UnitTestsactuallygetwritten• Producestestabledesigns• Thinkoutside-in, firstabouthowtouse,thenabouthowtodoit• GoodunitteststhatsupportRefactoring• RequirementsClarification&Understanding• Confidence (nofear)• Solutions thatfitlikeahandinaglove• Version1.0codethatyouarehappywith• ReducesDefects

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TDD– “Rediscovered”byKentBeck“TotheunknownauthorofthebookwhichIreadasaweird12-yearoldthatsuggestedyoutypeintheexpectedoutputtapefromarealinputtape,thencodeuntiltheactualresultsmatchedtheexpected result,thankyou,thankyou,thankyou.”

– KentBeck(Test-DrivenDevelopmentByExample)

THEENDQuestions?