TDD and S.O.L.I.D.; Two Ingredients For High Quality Software

TDD & S.O.L.I.D.Two ingredients for high-quality software
Dennis Doomen
dennis.doomen@avivasolutions.nl

About Me
Principal Consultant at Aviva Solutions
35 years
6-month daughter
12 years of experience
C++ origins
On .NET since 2001

Agenda
About quality
Test Driven Development & S.O.L.I.D
Demos & examples
Guidelines to get started

What is quality?
Or, how do you measure it?“I don't care howgoodyouthinkyour design is. If I can't walk in and write a test foranarbitrarymethod of yours in fiveminutes, itsnot as good as youthinkit is, and whetheryouknowitornot, you'repaying a pricefor it.”Michael Feathers, ObjectMentor

How?
Use coding guidelines
Apply common design principles
Test Driven Development
Refactoring
Use Design Patterns
Pair Programming
Socialize design & architecture

Test Driven Development
Is a design process
Tests are your first users
Tests can be your documentation
If TDD hurts then you're doing it wrong

S.O.L.I.D.
Single ResponsiblityPrinciple
Open ClosedPrinciple
LiskovSubstitutionPrinciple
Interface SeggregationPrinciple
DependencyInversionPrinciple

Demo
Attendee registration
TDDSingle Reponsibility Principle
Dependency Inversion Principle

What you have seen
TDD
Arrange-Act-Assert
Red-Green-Refactor
Mocking
Intention revealing tests
Single Responsibility Principle
Dependency Inversion Principles

Phases of unit testing
Refusing
Getting too excited
Testing everything!
Integration testing
Discover mocking
Mocking everything
Becoming effective

Example
Types of attendees
Open Closed Principle

Naive Solution

Better Solution

Best Solution

What you have seen
Open Closed Principle
Chain of Responsibility Pattern
Factory Method Pattern

Example
Billing
Liskov Substitution Principle

Naive Solution

Better Solution
new EmployeeBuilder().Build() ??

Best Solution

What you have seen
Liskov Substition Principle

Example
Event listening
Interface seggregation

Naive Solution

Better Solution

Best Solution

What you have seen
Interface Seggregation

Getting started guidelines
Test should be
Small and focused
Intention revealing
Repeatable
Have no side-effects
Independent
Test what you know now (and assemble the rest from those pieces)

Getting started guidelines
Mocking
Don't mock chatty interfaces
Don't have more than 2-3 mocks per test
Only mock your nearest neigbors
Keep your tail short
Isolate the ugly stuff
Conform to SOLID (and other principles)

Resources
xUnit Patternshttp://xunitpatterns.com/
Applying Domain Driven Design and Design Patternshttp://www.amazon.com/Applying-Domain-Driven-Design-Patterns-Examples/dp/0321268202
Jeremy D. Millerhttp://codebetter.com/blogs/jeremy.miller/default.aspxhttp://msdn.microsoft.com/en-us/magazine/cc720886.aspx
InfoQ Recommended TDD Tutorialshttp://www.infoq.com/news/2009/05/recommended-tdd-tutorials
Los Techies S.O.L.I.D. Principles E-Bookhttp://www.lostechies.com/content/pablo_ebook.aspx
C# 3.0 Coding Guidelineshttp://blog.avivasolutions.nl/archive/2009/03/06/new-coding-guidelines-for-c-3-0.aspx

Q&A
Emaildennis.doomen@avivasolutions.nl
Blogwww.dennisdoomen.net
Twitterwww.twitter.com/dennisdoomen

TDD and S.O.L.I.D.; Two Ingredients For High Quality Software

by Dennis Doomen on Sep 01, 2009

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