Test Driven Development - The Ajax Experience

73 Pages·2008·1.57 MB·English

Tes t D riven D evelopment with
YUI Tes t
Nicholas C . Zakas
P rincipal Front E nd E ngineer, Y ahoo!
Who's this g uy?
• P rincipal Front E nd E ngineer, Y ahoo!
Front P age
• Y UI C ontributor
• Author
Tes t D riven D evelopment
Design
Features
Run Write
Tests Tests
Write
Code
Why Tes t D riven D evelopment?
• No s uch thing as a s mall change
• S pecifically identifies tas ks
• Y ou unders tand your code the bes t
• Upfront inves tment pays off later
• Q A res ources are limited
• P eace of mind
Tes t D riven D evelopment
Design
Features
Run Write
Tests Tests
Write
Code
The R equirements
• Us ually, requirements are functional
• Trans late into interfaces (objects and
methods )
• D es cribe what each method s hould do in
terms of inputs and outputs
Design
Features
The R equirements
• Need: When a us ername is entered,
ignore s paces at the beginning and end
of text
• Trans lation: I need a trim function
• Trim function:
– R emove leading white space from the given
string and return result
– R emove trailing white space from the given
string and return result
Design
Features
Tes t D riven D evelopment
Design
Features
Run Write
Tests Tests
Write
Code
Unit Tes ts
• Tes t a s mall, is olated part of code (unit)
– Unit = method
• Tes t inputs and outputs
– One set at a time
• Tes t: “G iven this input, I expect this
output.”
Write
Tests
Unit Tes ting C omplaints
• R amp-up time
• Unfamiliar s yntax/concepts
• Tes t harnes s s etup is hard
• Writing tes ts takes too long
• C an't figure out what broke when a tes t
fails
Write
Tests