Identify and Exploit Behavioral Boundaries for Unit Testing

BW12Session6/8/164:15PM

IdentifyandExploitBehavioralBoundariesforUnitTesting

Presentedby:

RobMyers

AgileInstitute

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RobMyersAgileInstituteThefounderofAgileInstitute,RobMyersteachescoursesthatarealwaysablendoffunandpracticalhands-onlabs,“TrainingFromtheBackoftheRoom”learningtechniques,andrelevantfirst-personstoriesfrombothsuccessfulandnot-so-successfulagileimplementations.Withthirtyyearsofprofessionalexperiencewithsoftwaredevelopmentteams,RobhasbeentrainingandcoachingorganizationsinScrumandExtremeProgrammingsince1998.Hecurrentlyworkswithtinystart-upsandhugeFortune100multinationals,helpingthemwithculturalchangeandessentialpracticesfromScrum,kanban,XP,andlean.

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5 June 2016 © Agile Institute 2008-2016 1

Identify & Exploit Behavioral Boundaries

for Unit Testing Rob Myers

@agilecoach

Better Software West 08 June 2016

Café!


Unit Test A test of one smallest bit of behavior. Also known these days as a microtest.

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“As the tests get more specific, the code gets more generic.”

– Bob Martin

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“The more code you write without testing the behavioral

boundaries, the harder they are

to find & test later.”

– me

triangulation


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dial setting

perc

ent

man

ufac

ture

r m

axim

um

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Pretend java.util.Set is BROKEN!

We need our own Set class with the capabilities of creating unions & intersections; checking if a set is empty; and also if it is equal to, a superset of, or a subset of another set.



empty?

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@TestpublicvoidisEmptyWhenConstructed(){

Setset=newSet();assertThat(set.isEmpty(),is(true));

}


not empty

3

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@TestpublicvoidisNotEmptyWhenItemAdded(){

Setset=newSet();set.addElement(3);assertThat(set.isEmpty(),is(false));

}@TestpublicvoidisEmptyWhenConstructed(){

Setset=newSet();assertThat(set.isEmpty(),is(true));

}


@Test(expected=IllegalArgumentException.class)publicvoidshouldNotAcceptNegativeNumbers(){

Setset=newSet();set.addElement(-1);

}

-1

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A B

1 2

3 5

8 4

6 7

9


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booleansubsetOf(Setother){

returnsize()<=other.size();}booleansupersetOf(Setother){

returnsize()>=other.size();}


A B

1 2

3 5

8 4

6 7

9

C

10 11

12

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Hungover Intern Principle

We write the microtests that will warn a hung-over intern six months

from now as to why the implementation is the way it is—

however simple or complex, efficient or slow it may be.

*Protects against mistakes, not sabotage.

*

In order to be an acceptable password, a string must: q Have a length greater than 7 characters. q Contain at least one alphabetic character. q Contain at least one digit. q Contain a special character. q First character must be special or digit. 5 June 2016 © Agile Institute 2008-2016 22

Password Strength Checker

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12345678

Good Bad

1234567

1234567B 12345678

Rule

Length > 7

Has alpha

passw0rd password Has digit

passw0rd? passw0rd Has special

?passw0rd passw0rd? 1st special/digit 4password?


?passw0rd

Good Bad

?passw0

?passw0rd

?1234567

Rule

Length > 7

Has alpha

?passw0rd

?password Has digit

?passw0rd passw0rd Has special

?passw0rd passw0rd? 1st special/digit 4password?

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combinations


X Y Z

A C E

A D E

A C F

A D F

B C E

B D E

B C F

B D F

pair-wise testing


X Y Z

A C E

A D E

A C F

A D F

B C E

B D E

B C F

B D F

X Y Z

A C E

A D F

B D E

B C F

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Listen to the Microtests

If you have difficulty unit-testing something,

this is indicating an opportunity to improve the design.


Rule

+ bool passes(string pw)

PasswordStrengthChecker

+ bool isStrong( string password)

LengthGT7 HasDigit HasAlpha

HasSpecial FirstSpecialOrDigit

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12345678

Good Bad

1234567

A3, 3A, 3A3

3

Rule

Length > 7

Has alpha

3A, A3, A3A

A Has digit

AB$, A$B A Has special

$A, 3A A$, A3 1st special/digit


Rule




LengthGT7 HasDigit HasAlpha

HasSpecial FirstSpecialOrDigit

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Rule




MockRule

+ bool passes(string pw) + void setPassesTo(bool p) + bool passesWasCalled()

LengthGT7 HasAlpha

HasSpecial


Examples Boundary type

True / False Valid / Invalid Happy / Unhappy

Conditional

Iterative

Comparative Greater Than Less Than Before / After

Zero / One / Many Subtype

*

* Examples! Not intended as a comprehensive list.

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[email protected]

https://www.linkedin.com/in/robmyers64

@agilecoach