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Head First Fixture Replacement
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Kensuke Nagae
March 21, 2012
Programming
1
2.9k
Head First Fixture Replacement
ペパボ社内の RSpec 勉強会で Fixture Replacement について発表したスライドです。
Kensuke Nagae
March 21, 2012
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Transcript
Head First Fixture Replacement @kyanny
Disclaimer: Samples Are Not Smartest, Not Enough, Not Exactly Correct
Test Environment then Fixture then Fixture Replacement
Test Environment
Test Suite Requires Isolate Environment
Unified Environment
User.create assert User.count == 1 # SUCCESS
User.create # Oops! Someone Create User # POST /users/create assert
User.count == 1 # FAIL
Isolate Environment
mysql> show databases; +--------------------+ | Database | +--------------------+ | development
| | test | | production | +--------------------+
User.create # For Development Environment # POST /users/create assert User.count
== 1 # SUCCESS
Fixture
Fixture == Dummy Data for Tests
: ( user = User.create user.albums << Album.create user.albums <<
Album.create user.albums << Album.create assert user.albums.count >= 3
# fixtures/users.yml alice: id: 1 email:
[email protected]
bob: id: 2
email:
[email protected]
# fixtures/albums.yml one: user_id: 1 two: user_id: 1 three: user_id:
1
: ) fixtures :users fixtures :albums user = users(:alice) assert
user.albums.count >= 3
But... DRY
Fixture is Too Difficult To Maintain
Complex Association
# User has_many :bookmarks has_many :pages, :through => :bookmarks #
Page has_many :bookmarks has_many :users, :through => :bookmarks # Bookmark belongs_to :user belongs_to: page
# fixtures/users.yml alice: id: 1 email:
[email protected]
bob: id: 2
email:
[email protected]
# fixtures/pages.yml twitter: id: 1 url: http://twitter.com/ facebook: id: 2
url: http://facebook.com/
# fixtures/bookmarks.yml alice_twitter: user_id: 1 page_id: 1 bob_facebook: user_id: 2
page_id: 1 # Oops! Wrong id
bob = users(:bob) assert bob.pages.first.url == "http://facebook.com/" # FAIL
Complex Data
# fixtures/photos.yml one: album_id: 1 exif: | --- width: 1024
height: 768 f_number: 280/100
Fixture is Too Difficult To Maintain
Fixture Replacement
Fixture Replacement == Skeleton of Dummy Data for Tests
Fixture == Data itself Fixture Replacement == Skeleton of Data
# factories/users.rb Factory.define(:album) do |a| a.title "Album Title" a.password "Album
Password" end album = Factory.create(:album) album = Factory.create(:album, :title => "Happy Wedding")
# factories/users.rb Factory.define(:alice) do |u| u.email "
[email protected]
" end Factory.define(:bob) do
|u| u.email "
[email protected]
" end
# factories/users.rb Factory.sequence(:email) do |n| "user_#{n}@example.com" end Factory.define(:user) do |u|
u.email { Factory.next(:email) } end
Flexible
# factories/pages.rb Factory.define(:twitter) do |p| p.url "http://twitter.com/" end Factory.define(:facebook) do
|p| p.url "http://facebook.com/" end
# factories/users.rb Factory.define(:alice) do |u| u.pages {[ Factory(:twitter) ]} end
Factory.define(:bob) do |u| u.pages {[ Factory(:facebook) ]} end
bob = Factory.create(:bob) assert bob.pages.first.url == "http://facebook.com/" # SUCCESS
But... Flexible
Fixture Replacement is Not a Silver Bullet
Children w/ Independent Parent
# factories/albums.rb Factory.define(:album) do |a| a.user { Factory(:user) } end
Factory.define(:paid) do |a| a.user { Factory(:user) } end
3.times do album = Factory.create(:album) end paid = Factory.create(:paid) user
= paid.user assert user.albums.count == 4 # FAIL
user = Factory.create(:user) 3.times do Factory(:album, :user => user) end
Factory(:paid, :user => user) assert user.albums.count == 4 # SUCCESS
Not DRY
Proposal: Fixture w/ Fixture Replacement
Test Context Arrangement Recipebook
First, Use Fixture. Complex, Then Use Fixture Replacement.
# fixtures/users.yml alice: id: 1 bob: id: 2
# fixtures/albums.yml one: user_id: 1 two: user_id: 1 three: user_id:
1 four: user_id: 1
fixtures :all user = users(:alice) assert user.albums.count == 4 #
SUCCESS
# factories/photos.rb exif = { :width => 1024, :height =>
768 } Factory.define(:photo) do |p| p.exif { exif.to_yaml } end
photo = Factory.create(:photo) assert photo.exif[:width] == 1024 # SUCCESS
Use The Right Tool In The Right Place
http://www.func09. com/wordpress/archives/532 http://eblog.drecom.jp/entry/14 http://www.slideshare.net/moro/test- context-arrangement-recipebook http://d.hatena.ne. jp/a666666/20110220/1298135559
end
Kensuke Nagae blog.kyanny.me @kyanny