Test Driven Development

Clean Code that works!!!

Agenda

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Intro to TDD

TDD by example

Conclusions

Intro

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What is TDD

Developed (or rediscovered) by Kent Beck to encourage

simple design and inspire confidence.

Related to the test-first programming concepts of eXtrem

Programming

A software development process that relies on the

repetition of a very short development cicle

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The golden rules

Never write model code

unless you have a test that

requires it

Write new code only if an

automated test has failed

Eliminate duplication

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What's my motivation?

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COURAGE

Clean Code that works!!!

Managing fear

“I have a problem and I can't see the end from the beginning”

Fear says you to be carefull

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TDD mantra

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Benefits

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Programmers who wrote more tests tended to be more productive

Programmers using TDD rarely felt the need to invoke a debugger TDD offers validation of correctness and drives the design of a program

TDD offers the ability to take small steps Even if more code is required, the total code implementation time could be

shorter TDD can lead to more modularized, flexible and extensible code

Because no more code is written than necessary to pass a failing test case, tests tend to cover every code path.

TDD by example

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Multi Currency Money

11

Bond portfolio management system.

Company Shares Price Total

Pippo SpA 1000 25 25000

Pluto srl 400 100 40000

Total 65000

Multy currency report

Company Shar

es

Price Total

Pippo SpA 1000 25 EUR 25000 EUR

Gastone SaS 400 100 USD 40000 USD

Total 65000 EUR

Rates

From To Rate

USD EUR 2

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Conclusions

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TDD Best Practices I

Work only on one test at a time

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TDD Best Practices II

Write test assertions

self-explanatory

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TDD Best Practices III

Same structure for tests and

source code

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TDD Best Practices IV

Keep tests small

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TDD Best Practices V.I

integrate your code every few unit test and never

leave broken tests

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If you are working in a team...

TDD Best Practices V.II

end every day with a broken test

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If you are working alone...

Summary

TDD Mantra

TDD rhythm

Value Object pattern

Information Hiding principle

DRY principle

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Bibliography and references

Kent Beck – Test-Driven Development by Example, The Addison-Wesley Signature Series

Jason Gorma – Agile Java Development: Test-Driven Development using JUnit and Eclipse

WardsWiKi - http://c2.com/cgi/wiki?TestDrivenDevelopment

WardsWiKi - http://c2.com/cgi/wiki?DontRepeatYourself

www.testdriven.com

www.junit.com

www.bigthink.it/php/test-driven-development-prima-i-test-poi-il-codice

www.agiledata.org/essays/tdd.html

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Thank you for your attention!!!

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