© A L E X A N D R E C U VA V E R S I O N 2 . 0 0

Test Driven Design

Alexandre Cuva

• Agile Transition Coach, Scrum Master, Product Owner

• Management 3.0 & Certified Scrum Developer Trainer

• Event speaker

• Hermes Swiss Project Team Professional

• ITIL V3

“I coach teams and organization to become highly productive.”

http://www.slideshare.net/GToronto

Agile Transition Coach

Why should developers write tests?- 5 -

Common responses: “leave testing to QA” “developers are too busy” “developers don’t know how to test” “We don’t have bugs” “developers are intimately familiar with the structure

of the code and are not well-suited for testing it”

But- 6 -

“if developers don’t test. How do they know that they are producing quality software?”

Tests are a tool to help developers take responsibility for quality

Tests help making small steps and give immediate feedback

Test help maintain focus on measurable outcome of coding – producing the code that accomplishes a concrete objective

Kent Beck say Good unit tests …- 7 -

Express intent, not implementation detailsRun fast (they have short setups, run times,

and break downs)Run in isolation (reordering possible)Run in parallelUse data that makes them easy to read and

to understand

Testing- 8 -

Design

Implement

Test

TDD- 9 -

Design

Test

Implement

Test

TDD- 10 -

Design

Test

Implement

Test

How to do it- 11 -

Design: figure out what you want to doTest: write a test to express the design

It should FAILImplement: write the codeTest: run the test

It should PASS

Test Unit Framework- 12 -

Microsoft Test MSTest Included inside - VS2010 Professional- VS2008 Team System

NUnit Most Used Open SourceMore upToDate than MSTest

xUnit Fork from NUnitMost Used Open Source ?

Visual Studio- 13 -

Have always a separate project for your test. Unit Test : xxxTest ATDD : xxxAcceptanceTest BDD : xxxSpec Integration : xxxIntegrationTest

Visual Studio- 14 -

On Visual Studio : Create a Project “Test Project” Add new Test Select “Basic Unit Test”

Test- 15 -

int expected = 4; // Header

int result = Calculator.Add(2, 2); //Body

Assert.AreEqual(expected, result); //Footer

FAIL- 16 -

Implement- 17 -

public static int Add(int number1, int number2) { return number1 + number2; }

Test- 18 -

Iterate- 19 -

Design

Test

ImplementTest

Refactor

Try It !- 20 -

Write once, run often- 21 -

Write tests onceKeep them somewhere sensibleRun frequently (one click)No human inputMachine-parsable output

When should I use TDD- 22 -

AlwaysWrite tests for anything you feel that might

breakDesign of production code should always be

test-drivenNo need to write tests for APIs you don’t own

…

Two fundamental TDD rules (Kent Beck)- 23 -

Never write a single line of code unless you have a failing automated test.

Eliminate duplication

Refactoring improves design- 24 -

“Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure”

Martin Fowler

Question ?

25

- 26 -

Books

27

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http://ch.linkedin.com/in/cuvaalex

@cuvaalex (twitter)

http://agile-alexcuva.blogspot.ch (blog)

http://www.slideshare.net/GToronto

management30.com (book)