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Test Driven Developmenttdd.talks.makandra.commakandra GmbH

continued slides from chapter #2

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shopping_cart.feature, line 6

Expected to see "Item was added to cart"

...................................................................

.......................................... .........................

......................

157 scenarios (156 passed, 1 failed)

�Technical debt

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„Customers should be able to order without registration or login“

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„Customers should be able to order without registration or login“

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As a project progresses,

it accumulates technical debt

� Code is growing more coupled, but cleaning up is risky

� Error rates are rising

� Regressions:New features are breaking existing features

� Changes become increasingly expensive

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project progression

Fixing bugs, wrestling with old code

Implementing new featuresw

ork

ing

ho

urs

� �project progression

exp

en

ses

Credits: davenicolette.net

� �project progression

exp

en

ses

Fixing bugs

New features

pla

nn

ed

pro

ject

lif

esp

an

Credits: davenicolette.net

� �project progression

exp

en

ses

Fixing bugs

New features

pla

nn

ed

pro

ject

lif

esp

an

Credits: davenicolette.net

� �project progression

exp

en

ses

Fixing bugs

New features

de

ath

of

the

pro

ject

pla

nn

ed

pro

ject

lif

esp

an

Credits: davenicolette.net

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Credits: davenicolette.net

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original code

cost of next change

C

Credits: davenicolette.net

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original code

cost of next change

C

code after change

cost of next change

C + n

Credits: davenicolette.net

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original code

cost of next change

C

code after change

cost of next change

C + n

refactored code

cost of next change

C

Credits: davenicolette.net

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Tests enable continuous reduction

of technical debt

� In the presence of tests, code refactoring is easy and riskless

� Technical debt is repaid in small installment over the course of the project

� Problems are mitigated before they become unmaintainable

� �project progression

exp

en

ses

Fixing bugs

New features

pla

nn

ed

pro

ject

lif

esp

an

Credits: davenicolette.net

� �project progression

exp

en

ses

Fixing bugs

New features

pla

nn

ed

pro

ject

lif

esp

an

Credits: davenicolette.net

�Fast releases

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Manual QA sucks

� Manually testing a release is time-consuming

� As the number of features grows, so does the time required to manually test for regressions

� A natural reaction is to release less often(„big bang releases“)

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R 1.0 R 1.2

QAdevelopment QAdevelopment

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Unreleased features are worthless

� Only released features add value to the client's business

� Only released features will generate feedback

� Code ages while requirements keep evolving

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Test-assisted QA enables fast delivery

� Manual QA for new features only

� Minimizes a feature's lead time from commission to release

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QAdevelopment QAdevelopment

R 1.0 R 1.2

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QAdevelopment QAdevelopment

R 1.0 R 1.2

development with automated tests

F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11

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this presentation continues with chapter #3 attdd.talks.makandra.com

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„dummies“ by greg westfall.www.flickr.com/photos/imagesbywestfall/3658162161/

„Day 4 – Paying off debt“ by quaziewww.flickr.com/photos/quazie/578252290/

„where to?“ by limaoscarjulietwww.flickr.com/photos/limaoscarjuliet/822938133/

„20100509 Kinetic Spring 086“ by cygnus921www.flickr.com/photos/cygnus921/4592767178/

„Hamburg Nightlights“ by eriwstwww.flickr.com/photos/eriwst/3483623571/

Illustrations

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