TestDrivenDevelopment

WhatisTDD• It'sadevelopmenttechniquebasedonashortdevelopment

process• It'sawaytodeeplyanalyzetheexpectedbehaviorofasoftware• It'sameantoimprovethequalityofthesourcecode• It'sapracticetoenhancethedocumentationofasoftware• It'sawaytoensureasaferwaytomodifythesoftwarebehavior

TDDandUnitTests

Unittestscanbewrittenbeforewritingthecode,afterthecodehasbeenwrittenorduringthedevelopment

• UnitTestingreferstowhatyouaretesting,TDDtowhenyouaretesting

• UnitTestingmeans,well,testingindividualunitsofbehavior

TheDintheMiddle• Youlettheteststodriveyou• Theteststellyouwhattodo,whattodonext,what'sdone• ThetestsaretheskeletonoftheAPIdesign

TDDWorkflow

TDDWorkflowTDDiswritingatestwhichwillfail,thenwritingtheminimum

amountofcoderequiredtomakeitrun,thenrefactoringthecodetomakeitclean

TheDattheEnd• It'ssupposedtomeandevelopmentbutoriginallywassupposed

tomeandesign• TestDrivenDesignisthedisciplineofusingUnitTesting(or

othertests)todesignthesoftware• Workingonabetterdesignit'spossibletoimprovethequalityof

thesoftware

SmallandTestable• Methodsandfunctionsshouldbesimpleinordertobetestable• Generallyspeaking,thecodeneededtosatisfyatestisusuallyaverysmallchunkofcode• AsaresultthepublicAPIaresimpleandeasytomaintain

TestDoubleThegeneralnameforobjectsusedtoreplacerealcomponentservers

fortestingpurposes

• Dummy,anobjectwithoutanyspecificimplementation• Stub,anobjectwithinterfaceorminimalimplementation

• Spy,astepupfromstubbecauseitrecordswhichobjectuseditself

• Fake,anobjectwithamorecompleximplementation• Mock,anobjectdynamicallycreatedbyalibrary(e.g.

http://sinonjs.org)

CommonSentences• “Itcoststoomuchtime,we’dbetterfixthesebugsfirst”

• “Oursystemistoobigforunittests”• “Wejustoughttobemorecarefulnottointroducebugs,that

willhelpusalot”• “Oursystemisnotsuitedforunittests”

• “WehaveaQA-teamthatwilldetecterrors”

TDDandQA• Testdrivendevelopmentisnotaqualityassurancemethod• Mostpeopleassociate"testing"with"qualityassurance"

• WithTDDyouwritecodeusingtestsasatool,theQAteamsearchesbugsusingthesametestsasatool

BestPractices

Assertions• Assertionsarestatementsthatperformanactualcheckonthesoftware’soutput• Asinglefunctioncalledassertisenoughtoexpressanycheck• TDDlibrarieshavemanyassertfunctionsforspecificneeds(assertFalse,assertEqual,s,etc.)• Asingleassertshouldbeusedineachtest• Anassertfailureshouldaddaclearmessagetothetestlogs

IntegrationTesting• Amid-leveltestingactivitythatverifiesacertainsetofmodulesworkcorrectlytogether• Integrationtestsarelikeunittestswithoutusingtestdoublesforsomedependencies

Source&TestsSeparation

PicktheFirstTest• Carefullyreadtherequirementsandeventuallysplitthemifneeded• Choosearequirementandwritealistoftestsforthisrequirement• Selectatestthatisatomicandwellisolated• Trytoprioritizethem(e.g.testfirstusercreationthanlogin!)

WritetheAssertionFirst

Determinehowthespecification(i.e.thetest)isgoingtobevalidated

FirstTimeFailure• Howtotestsomethingthatdoesn'texist?• Byaddingmethodsorfunctionstotestdevelopersstarttodesignfirstthecode

UnitTesting(UnitTestingreferstowhatyouaretesting,TDDtowhenyouare

testing)

Glossary

Glossary• Unit,thesmallestpieceofcodesoftwarethatcanbetestedin

isolation• Assertion,it'sapredicatethatstatestheprogrammer’s

intendedstateofasystem• Integrationtest,atestthatgooutsidethecurrentprocess

interactingwithsomethingelse• Interactiontest,atestonthewaythatobjectsworktogether• Fake,anystand-inobjectthat'susedinsteadoftherealthing• Stub,astand-inobjectthatprovidesadependencyrequiredby

thecodeundertest• Mock,asimulatedobjectthatmimicsaspecificbehavior

IndividualUnits• Sourcecodeistestedtounderstandifitcanbeusedbyother

partofthesoftware• Testcasesareseparatedandindependentbyeachother

• Methodstubs,mockobjectsandfakesdatacanbeusedtorunthetestsinisolation

Benefits• Helpsfindingproblemsearly

• Facilitateschanges(i.e.regressionstesting)• Simplifiesintegration

• Improvesthedocumentation

Limitations• Unittestingwillnotcatcheveryerrorintheprogram

• Integrationerrorswillbenotcatchbecausethetestitselfbydefinitiontestonlytheunit

• Codecoveragedoesn'tprovethesoftwareisworking• It'stimeconsuming

CommonChallenges• Settinguprealisticandusefultests

• Testingasynchronouscode• Testingprivatemethods• Writingflexibletests

• Effectivenames

Usefulness• Definerelevantinitialconditions

• Testshavetoexercisingthecodeinarealisticcontext• Avoidunnecessarypreconditions

• Don’tunit-testconfigurationsettings

Flexibility• Testsshouldneveroverspecifythebehaviorofthetargetcode• Testsshouldnevertestmorethanoncethesamecode(i.e.

don'trepeatyourself!)• Alwaysuseonlydatarelevanttoaparticulartestinthetest• Consideralwayshowtopassinputdata(e.g.Builderpattern)

AsyncCode• Themainissueistokeepthetestblockeduntiltheasynccode

hasbeenexecuted• Youcanrepeatedlypollingthetargetsystemforastatechange

(i.e.Sampling)• Youcanuseanevent-basedassertionthatwaitsforaneventby

blockingonamonitoruntilitgetsnotifiedortimesout(i.e.Listening)

PrivateMethods

Eventshandler,alsoifprivate,areyourpublicAPI

• Putthetestsintheclassyouwanttotest• Putthetestsinanotherclass/sourcefile&exposetheprivate

methodsyouwanttotestaspublicmethods

Naming• Thenameshouldclearlyindicatethetestedfeature

• Thetestnameshouldindicateswhattheunitdoesnotwhattheunitis

• Thetestnameshouldsaysomethingaboutthemotivationforthescenario

• UsetheTestDoxconventionwhereeachtestnamereadslikeasentence

AcceptanceTestDriven

Development

KeyFeatures• ATDDisapracticeinwhichthewholeteamcollaboratively

discussesrequirementsacceptability• ATDD,likeTDD,involvescreatingtestsbeforecode

• Theacceptanceteststhenbecomelikeexecutablerequirements

ExpectedBenefits• ATDDresultsinapplicationsdesignedtobeeasiertotest

• ATDDfavorsthecreationofinterfacesspecifictofunctionaltesting

• ATDDclarifytoalltheteammemberswhicharethecustomerexpectations

ATDDandUnitTesting

• ATDDdoesn'timplytoremoveunittestingfromthedevelopmentcycle

• ATDDimpliestheusageoftoolstoautomatethefunctionaltestingexecution(e.g.FitNess,Cucumber,Rspec)

TestingPyramid

Software

SoftwareRequirements

Asa<role>Iwantto<goal>sothat<motivation>

• Userstoriesarethecentralaxisaroundwhichasoftwareprojectrotates

• UserstoriesexpressrequirementsintermsofTheRole,TheGoal,andTheMotivation

• Userstoriesaren’texhaustiverequirementsspecifications

AcceptanceCriteria• Asetofconditionstherequirementmustfitintobeconsidered

done• It'stheresultofaconversationwiththecustomer(orproduct

owner)• It'sawaytodescribethetestsarequirementshouldpass

WritingAcceptanceCriteria

• AnacceptancecriteriashouldcontainanActor,aVerbandanObservableResult

• Anacceptancecriteriadescribeapre-condtionwhenanactorshouldperformanactionandobtaintheexpectedresult(e.g.

mandatoryfields)• Anacceptancecriteriashouldbealsoidentifyperformances

expectations

AcceptanceTests

Concreteexamples,concretebehavior,noambiguity

• Aformaldescriptionofthebehaviorofasoftwareproductexpressedasanexample

• Arethecombinationofacceptancecriteriaandrealexamples(i.e.dataandscenarios)

ATDDCycle

ATDDCycle

BehaviorDrivenDevelopment

KeyFeatures• Helptowriteteststhatreflectthebehaviordesiredbythe

stakeholders• UsesaUbiquitousLanguagethatcanbeunderstoodbyboththe

developerandthecustomer

TestDifferent• Unittestingforcedeveloperstothinkintermsoftestsandassertionswhilebehaviordrivendevelopmentbringthemto

considertestsaspartofspecification• Whenyourealizethatit'sallaboutspecifyingbehaviorandnot

writingtests,yourpointofviewshifts

It’sStillTDD?NothinginBehavior-DrivenDevelopmentchangesTestDriven

Development’smechanics(i.e.writethetest->passit->refactor)

BDDandCodeDesign

• Unittestingisoftenspecificallyaboutthedesignofcodeunitsandmodulessuchasclasses

• BDDisalsoconcernedwithunitdesign,butaddressesabroaderrangeofdesignconcerns

BDDandAcceptanceCriteria

• Acceptancecriteriaaretransformedintolower-levelspecificationswrittenincode,andexecutedusingatestingor

specificationframework

SignofUse• Significantportionof"functionaldocumentation"isintheformofUserStoriesaugmentedwithexecutablescenariosorexamples• Insteadofreferringto"tests",teammemberswillpreferthe

terms"scenario"and"specification"• Testsareameantodefinethespecificationsofthebehaviorof

aModule

CommonIssues• BDDrequiresfamiliaritywithagreaterrangeofconceptsthan

UnitTestingdoes• BDDdon'trequiresatthebeginningparticulartoolsor

programminglanguages,andisprimarilyaconceptualapproach• BDDrequiresadifferentdevelopmentcycle

BDDCycle

ContextandSpecifications

• Setsofrelatedobservations(tests)willbegatheredintocontexts

• Contextsaren’tsimplyarbitrarygroupings,theyrepresentcohesiveandconsistentcircumstancesthatsoftwaremodulescan

befoundin• SpecificationsarethetestswrittenusingaBDDtesting

framework

EffectiveScenarios• Captureasummaryscenario• Identifyactorsandtheirgoals

• Sentencesshouldbeinsequentialorder• Eachsentenceshouldhaveanactorperforminganaction

UnitTesting,ATDDandBDD

BDDisanevolutionoftest-drivendevelopmentthatenhanceandenforcethepracticesderivingfromunittestingandacceptance

testing

TDD===BDD

TestsAnatomy

UnitTeststest("prettydatebasics",function(){varnow="2008/01/2822:25:00";equal(prettyDate(now,"2008/01/2822:24:30"),"justnow");equal(prettyDate(now,"2008/01/2822:23:30"),"1minuteago");equal(prettyDate(now,"2008/01/2821:23:30"),"1hourago");equal(prettyDate(now,"2008/01/2722:23:30"),"Yesterday");equal(prettyDate(now,"2008/01/2622:23:30"),"2daysago");equal(prettyDate(now,"2007/01/2622:23:30"),undefined);});

ATDDTests

BDDTestsfunctionaddValues(a,b){returna+b;}

describe("addValues(a,b)function",function(){it("shouldequal3",function(){expect(addValues(1,2)).toBe(3);});it("shouldequal3.75",function(){expect(addValues(1.75,2)).toBe(3.75);});it("shouldNOTequal'3'asaString",function(){

Jasmine(JavaScripttestingsuite)

JasmineProvides• AnaturalBDDsyntaxfororganizingthetestlogic

• Asynchronoustestingsupport• Mocksobject

• Spies• Custommatchers

SampleTestdescribe("Helloworld",function(){it("sayshello",function(){expect(helloWorld()).toEqual("Helloworld!");});});

Suite• describe("Helloworld"...)iswhatiscalledasuite• Thenameofthesuite(“Helloworld”inthiscase)definesacomponentofyourapplication

Spec• Insideofthatsuite(technically,insideofananonymous

function),istheit()block• Thisiscalledaspecification,oraspecforshort

Matcher• Inthiscase,you’retestingifhelloWorld()doesindeedreturn

"Helloworld!"• Thischeckiscalledamatcher...Jasminesupportsseveralmatchers!

Specs.htmlItcontainsfourscripttags:

• ThefirstsectionincludestheJasminetestrunnerfiles• Inthenexttwosections,youreferenceyourJavaScriptcodeto

betestedaswellasthetests• Thefourthrunsthetests

AsyncCallsit("doesanasynchronouscall",function(){

exampleAsyncCall(function(response){expect(response).toContain("somethingexpected");done();});

});RunningTestswith

RunningTestswithGrunt

• AJavaScripttaskrunner• Aprojectscaffoldingtool• Useittoautomatecommontaskexecutionexecution• Configurablepluginssuchasrequire.js,handlebar,jasmine,etc.

• Configurablepluginssuchasrequire.js,handlebar,jasmine,etc.

UsingGrunt• Firstofallinstallgruntcommandlinetoolnpminstall-ggrunt-cli

• Mostgrunt-inittemplateswillautomaticallycreateapackage.jsonfile

• Installgruntanthepluginsnpminstallgrunt--save-dev• Installthejasminepluginnpminstallgrunt-contrib-jasmine--save-dev

TheGrunt.jsFilemodule.exports=function(grunt){'usestrict';grunt.initConfig({jasmine:{src:'src/**/*.js',options:{specs:'spec/**/*.js',template:require('grunt-template-jasmine-istanbul'),templateOptions:{coverage:'reports/coverage.json',report:'reports/coverage'}

Questions&Answers

Links

Links• http://msdn.microsoft.com/en-us/magazine/cc163358.aspx

• http://guide.agilealliance.org/guide/atdd.html• http://guide.agilealliance.org/guide/acceptance.html

• http://www.codemag.com/article/0805061• http://www.slideshare.net/nashjain/acceptance-test-driven-

development-350264• http://testobsessed.com/wp-

content/uploads/2011/04/atddexample.pdf• http://programmers.stackexchange.com/questions/135218/what-

is-the-difference-between-bdd-and-tdd• http://www.slideshare.net/emwendelin/test-your-javascriptMyLatestBook

• http://www.slideshare.net/emwendelin/test-your-javascriptMyLatestBook

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