Prelude
Style is what separates the good from the great.
-- Bozhidar Batsov
The goal of this guide is to present a set of best practices and style prescriptions for Ruby on Rails 3 development. It's a complementary guide to the already existing Ruby coding style guide.
While in the guide the section Testing Rails applications is after Developing Rails applications I truly believe that Behaviour-Driven Development (BDD) is the best way to develop software. Keep that in mind.
Rails is an opinionated framework and this is an opinionated guide. We believe that RSpec is superior to Test::Unit, and Scss is superior to CSS and. So don't expect to find any Test::Unit or CSS advice in here.
Some of the advice here is applicable only to Rails 3.1+.
This is the guide we use internally, for our own apps, at Skroutz.
You can also check out the Ruby coding style guide and the CSS coding style guide.
You can generate a PDF or an HTML copy of this guide using Transmuter.
Table of Contents
Developing Rails applications
Configuration
-
Put custom initialization code in
config/initializers
. The code in initializers executes on application startup. -
The initialization code for each gem should be in a separate file with the same name as the gem, for example
carrierwave.rb
,active_admin.rb
, etc. -
Adjust accordingly the settings for development, test and production environment (in the corresponding files under
config/environments/
)-
Mark additional assets for precompilation (if any):
```Ruby # config/environments/production.rb # Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added) config.assets.precompile += %w( rails_admin/rails_admin.css rails_admin/rails_admin.js ) ```
-
-
Create an additional
staging
environment that closely resembles theproduction
one.
Routing
-
When you need to add more actions to a RESTful resource (do you really need them at all?) use
member
andcollection
routes.# bad get 'subscriptions/:id/unsubscribe' resources :subscriptions # good resources :subscriptions do get 'unsubscribe', :on => :member end # bad get 'photos/search' resources :photos # good resources :photos do get 'search', :on => :collection end
-
If you need to define multiple
member/collection
routes use the alternative block syntax.resources :subscriptions do member do get 'unsubscribe' # more routes end end resources :photos do collection do get 'search' # more routes end end
-
Use nested routes to express better the relationship between ActiveRecord models.
class Post < ActiveRecord::Base has_many :comments end class Comments < ActiveRecord::Base belongs_to :post end # routes.rb resources :posts do resources :comments end
-
Use namespaced routes to group related actions.
namespace :admin do # Directs /admin/products/* to Admin::ProductsController # (app/controllers/admin/products_controller.rb) resources :products end
-
Never use the legacy wild controller route. This route will make all actions in every controller accessible via GET requests.
# very bad match ':controller(/:action(/:id(.:format)))'
Controllers
- Keep the controllers skinny - they should only retrieve data for the view layer and shouldn't contain any business logic (all the business logic should naturally reside in the model).
- Each controller action should (ideally) invoke only one method other than an initial find or new.
- Share no more than two instance variables between a controller and a view.
- Use Decorators to enhance your models with presentational logic, draper is the suggested gem for this purpose.
Models
-
Introduce non-ActiveRecord model classes freely.
-
Name the models with meaningful (but short) names without abbreviations.
-
If you need model objects that support ActiveRecord behavior like validation use the ActiveAttr gem.
class Message include ActiveAttr::Model attribute :name attribute :email attribute :content attribute :priority attr_accessible :name, :email, :content validates_presence_of :name validates_format_of :email, :with => /^[-a-z0-9_+\.]+\@([-a-z0-9]+\.)+[a-z0-9]{2,4}$/i validates_length_of :content, :maximum => 500 end
For a more complete example refer to the RailsCast on the subject.
ActiveRecord
-
Avoid altering ActiveRecord defaults (table names, primary key, etc) unless you have a very good reason (like a database that's not under your control).
-
Group macro-style methods (
has_many
,validates
, etc) in the beginning of the class definition. -
Prefer
has_many :through
tohas_and_belongs_to_many
. Usinghas_many :through
allows additional attributes and validations on the join model.# using has_and_belongs_to_many class User < ActiveRecord::Base has_and_belongs_to_many :groups end class Group < ActiveRecord::Base has_and_belongs_to_many :users end # prefered way - using has_many :through class User < ActiveRecord::Base has_many :memberships has_many :groups, through: :memberships end class Membership < ActiveRecord::Base belongs_to :user belongs_to :group end class Group < ActiveRecord::Base has_many :memberships has_many :users, through: :memberships end
-
Always use the new "sexy" validations.
-
When a custom validation is used more than once or the validation is some regular expression mapping, create a custom validator file.
# bad class Person validates :email, format: { with: /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i } end # good class EmailValidator < ActiveModel::EachValidator def validate_each(record, attribute, value) record.errors[attribute] << (options[:message] || 'is not a valid email') unless value =~ /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i end end class Person validates :email, email: true end
-
All custom validators should be moved to a shared gem.
-
Use named scopes freely.
class User < ActiveRecord::Base scope :active, -> { where(active: true) } scope :inactive, -> { where(active: false) } scope :with_orders, -> { joins(:orders).select('distinct(users.id)') } end
-
Wrap named scopes in
lambdas
to initialize them lazily.# bad class User < ActiveRecord::Base scope :active, where(active: true) scope :inactive, where(active: false) scope :with_orders, joins(:orders).select('distinct(users.id)') end # good class User < ActiveRecord::Base scope :active, -> { where(active: true) } scope :inactive, -> { where(active: false) } scope :with_orders, -> { joins(:orders).select('distinct(users.id)') } end
-
When a named scope defined with a lambda and parameters becomes too complicated, it is preferable to make a class method instead which serves the same purpose of the named scope and returns an
ActiveRecord::Relation
object. Arguably you can define even simpler scopes like this.class User < ActiveRecord::Base def self.with_orders joins(:orders).select('distinct(users.id)') end end
-
Beware of the behavior of the
update_attribute
method. It doesn't run the model validations (unlikeupdate_attributes
) and could easily corrupt the model state. -
Use user-friendly URLs. Show some descriptive attribute of the model in the URL rather than its
id
. There is more than one way to achieve this:-
Override the
to_param
method of the model. This method is used by Rails for constructing a URL to the object. The default implementation returns theid
of the record as a String. It could be overridden to include another human-readable attribute.class Person def to_param "#{id} #{name}".parameterize end end
In order to convert this to a URL-friendly value,
parameterize
should be called on the string. Theid
of the object needs to be at the beginning so that it can be found by thefind
method of ActiveRecord. -
Use the
friendly_id
gem. It allows creation of human-readable URLs by using some descriptive attribute of the model instead of itsid
.class Person extend FriendlyId friendly_id :name, use: :slugged end
Check the [gem documentation](https://github.com/norman/friendly_id) for more information about its usage.
-
Rendering Custom Formats
- When the response is in a format different from the existing ones (XML and JSON) or some additional parsing of these formats is necessary, create your own custom renderer.
ActionController::Renderers.add :csv do |obj, options|
filename = options[:filename] || 'data'
str = obj.respond_to?(:to_csv) ? obj.to_csv : obj.to_s
send_data str, type: Mime::CSV, disposition: "attachment; filename=#{filename}.csv"
end
The renderer in action:
def show
@csvable = Csvable.find(params[:id])
respond_to do |format|
format.html
format.csv { render csv: @csvable, filename: @csvable.name }
end
end
More about ActionController::Renderers
Migrations
-
Keep the
schema.rb
orstructure.sql
under version control. -
Use
rake db:schema:load
orrake db:structure:load
instead ofrake db:migrate
to initialize an empty database. -
Use
rake db:test:prepare
to update the schema of the test database. -
Avoid setting defaults in the tables themselves (unless the db is shared between several applications). Use the model layer instead.
def amount self[:amount] or 0 end
While the use of
self[:attr_name]
is considered fairly idiomatic, you might also consider using the slightly more verbose (and arguably more readable)read_attribute
instead:def amount read_attribute(:amount) or 0 end
-
When writing constructive migrations (adding tables or columns), use the new Rails 3.1 way of doing the migrations - use the
change
method instead ofup
anddown
methods.# the old way class AddNameToPerson < ActiveRecord::Migration def up add_column :persons, :name, :string end def down remove_column :person, :name end end # the new prefered way class AddNameToPerson < ActiveRecord::Migration def change add_column :persons, :name, :string end end
Views
- Never call the model layer directly from a view.
- Never make complex formatting in the views, export the formatting to a method in the view helper or the model.
- Mitigate code duplication by using partial templates and layouts.
- Add
client side validation
for the custom validators. The steps to do this are:
-
Declare a custom validator which extends
ClientSideValidations::Middleware::Base
```Ruby module ClientSideValidations::Middleware class Email < Base def response if request.params[:email] =~ /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i self.status = 200 else self.status = 404 end super end end end ```
-
Create a new file
public/javascripts/rails.validations.custom.js.coffee
and add a reference to it in yourapplication.js.coffee
file:``` # app/assets/javascripts/application.js.coffee #= require rails.validations.custom ```
-
Add your client-side validator:
```Ruby #public/javascripts/rails.validations.custom.js.coffee clientSideValidations.validators.remote['email'] = (element, options) -> if $.ajax({ url: '/validators/email.json', data: { email: element.val() }, async: false }).status == 404 return options.message || 'invalid e-mail format' ```
-
Internationalization
-
No strings or other locale specific settings should be used in the views, models and controllers. These texts should be moved to the locale files in the
config/locales
directory. -
When the labels of an ActiveRecord model need to be translated, use the
activerecord
scope:en: activerecord: models: user: Member attributes: user: name: "Full name"
Then
User.model_name.human
will return "Member" andUser.human_attribute_name("name")
will return "Full name". These translations of the attributes will be used as labels in the views. -
Separate the texts used in the views from translations of ActiveRecord attributes. Place the locale files for the models in a folder
models
and the texts used in the views in folderviews
.-
When organization of the locale files is done with additional directories, these directories must be described in the
application.rb
file in order to be loaded.```Ruby # config/application.rb config.i18n.load_path += Dir[Rails.root.join('config', 'locales', '**', '*.{rb,yml}')] ```
-
-
Place the shared localization options, such as date or currency formats, in files under the root of the
locales
directory. -
Use the short form of the I18n methods:
I18n.t
instead ofI18n.translate
andI18n.l
instead ofI18n.localize
. -
Use "lazy" lookup for the texts used in views. Let's say we have the following structure:
en: users: show: title: "User details page"
The value for
users.show.title
can be looked up in the templateapp/views/users/show.html.haml
like this:= t '.title'
-
Use the dot-separated keys in the controllers and models instead of specifying the
:scope
option. The dot-separated call is easier to read and trace the hierarchy.# use this call I18n.t 'activerecord.errors.messages.record_invalid' # instead of this I18n.t :record_invalid, :scope => [:activerecord, :errors, :messages]
-
More detailed information about the Rails i18n can be found in the [Rails Guides] (http://guides.rubyonrails.org/i18n.html)
Assets
Use the assets pipeline to leverage organization within your application.
- Reserve
app/assets
for custom stylesheets, javascripts, or images. - Third party code such as jQuery or bootstrap
should be placed in
vendor/assets
. - Use bower to manage asset versions and dependencies and prefer it over gemified versions of assets (e.g. jquery-rails).
Mailers
-
Name the mailers
SomethingMailer
. Without the Mailer suffix it isn't immediately apparent what's a mailer and which views are related to the mailer. -
Provide both HTML and plain-text view templates.
-
Enable errors raised on failed mail delivery in your development environment. The errors are disabled by default.
# config/environments/development.rb config.action_mailer.raise_delivery_errors = true
-
Use
smtp.gmail.com
for SMTP server in the development environment (unless you have local SMTP server, of course).# config/environments/development.rb config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', # more settings }
-
Provide default settings for the host name.
# config/environments/development.rb config.action_mailer.default_url_options = {host: "#{local_ip}:3000"} # config/environments/production.rb config.action_mailer.default_url_options = {host: 'your_site.com'} # in your mailer class default_url_options[:host] = 'your_site.com'
-
If you need to use a link to your site in an email, always use the
_url
, not_path
methods. The_url
methods include the host name and the_path
methods don't.# wrong You can always find more info about this course = link_to 'here', url_for(course_path(@course)) # right You can always find more info about this course = link_to 'here', url_for(course_url(@course))
-
Format the from and to addresses properly. Use the following format:
# in your mailer class default from: 'Your Name <info@your_site.com>'
-
Make sure that the e-mail delivery method for your test environment is set to
test
:# config/environments/test.rb config.action_mailer.delivery_method = :test
-
The delivery method for development and production should be
smtp
:# config/environments/development.rb, config/environments/production.rb config.action_mailer.delivery_method = :smtp
-
When sending html emails all styles should be inline, as some mail clients have problems with external styles. This however makes them harder to maintain and leads to code duplication. There are two similar gems that transform the styles and put them in the corresponding html tags: premailer-rails3 and roadie.
-
Sending emails while generating page response should be avoided. It causes delays in loading of the page and request can timeout if multiple email are send. To overcome this emails can be send in background process with the help of delayed_job gem.
Bundler
-
Put gems used only for development or testing in the appropriate group in the Gemfile.
-
Use only established gems in your projects. If you're contemplating on including some little-known gem you should do a careful review of its source code first.
-
OS-specific gems will by default result in a constantly changing
Gemfile.lock
for projects with multiple developers using different operating systems. Add all OS X specific gems to adarwin
group in the Gemfile, and all Linux specific gems to alinux
group:# Gemfile group :darwin do gem 'rb-fsevent' gem 'growl' end group :linux do gem 'rb-inotify' end
To require the appropriate gems in the right environment, add the following to
config/application.rb
:platform = RUBY_PLATFORM.match(/(linux|darwin)/)[0].to_sym Bundler.require(platform)
-
Do not remove the
Gemfile.lock
from version control. This is not some randomly generated file - it makes sure that all of your team members get the same gem versions when they do abundle install
.
Priceless Gems
One of the most important programming principles is "Don't reinvent the wheel!". If you're faced with a certain task you should always look around a bit for existing solutions, before unrolling your own. Here's a list of some "priceless" gems (all of them Rails 3.1 compliant) that are useful in many Rails projects:
- active_admin - With ActiveAdmin the creation of admin interface for your Rails app is child's play. You get a nice dashboard, CRUD UI and lots more. Very flexible and customizable.
- capybara - Capybara aims to simplify the process of integration testing Rack applications, such as Rails, Sinatra or Merb. Capybara simulates how a real user would interact with a web application. It is agnostic about the driver running your tests and currently comes with Rack::Test and Selenium support built in. HtmlUnit, WebKit and env.js are supported through external gems. Works great in combination with RSpec & Cucumber.
- carrierwave - the ultimate file upload solution for Rails. Support both local and cloud storage for the uploaded files (and many other cool things). Integrates great with ImageMagick for image post-processing.
- client_side_validations - Fantastic gem that automatically creates JavaScript client-side validations from your existing server-side model validations. Highly recommended!
- compass-rails - Great gem that adds support for some css frameworks. Includes collection of sass mixins that reduces code of css files and help fight with browser incompatibilities.
- cucumber-rails - Cucumber is the premium tool to develop feature tests in Ruby. cucumber-rails provides Rails integration for Cucumber.
- devise - Devise is full-featured authentication solution for Rails applications. In most cases it's preferable to use devise to unrolling your custom authentication solution.
- fabrication - a great fixture replacement (editor's choice).
- factory_girl - an alternative to fabrication. Nice and mature fixture replacement. Spiritual ancestor of fabrication.
- faker - handy gem to generate dummy data (names, addresses, etc).
- feedzirra - Very fast and flexible RSS/Atom feed parser.
- friendly_id - Allows creation of human-readable URLs by using some descriptive attribute of the model instead of its id.
- guard - fantastic gem that monitors file changes and invokes tasks based on them. Loaded with lots of useful extension. Far superior to autotest and watchr.
- kaminari - Great paginating solution.
- machinist - Fixtures aren't fun. Machinist is.
- rspec-rails - RSpec is a replacement for Test::MiniTest. I cannot recommend highly enough RSpec. rspec-rails provides Rails integration for RSpec.
- simple_form - once you've used simple_form (or formtastic) you'll never want to hear about Rails's default forms. It has a great DSL for building forms and no opinion on markup.
- simplecov-rcov - RCov formatter for SimpleCov. Useful if you're trying to use SimpleCov with the Hudson contininous integration server.
- simplecov - code coverage tool. Unlike RCov it's fully compatible with Ruby 1.9. Generates great reports. Must have!
- spork - A DRb server for testing frameworks (RSpec / Cucumber currently) that forks before each run to ensure a clean testing state. Simply put it preloads a lot of test environment and as consequence the startup time of your tests in greatly decreased. Absolute must have!
- sunspot - SOLR powered full-text search engine.
- active-model-serializers - Brings convention over configuration to your JSON generation.
- teaspoon - A JavaScript test runner built for Rails. It can run tests in the browser and headless using PhantomJS or Selenium WebDriver.
This list is not exhaustive and other gems might be added to it along the road. All of the gems on the list are field tested, have active development and community and are known to be of good code quality.
Flawed Gems
This is a list of gems that are either problematic or superseded by other gems. You should avoid using them in your projects.
- rmagick - this gem is notorious for its memory consumption. Use minimagick instead.
- autotest - old solution for running tests automatically. Far inferior to guard and watchr.
- rcov - code coverage tool, not compatible with Ruby 1.9. Use SimpleCov instead.
- therubyracer - the use of this gem in production is strongly discouraged as it uses a very large amount of memory. I'd suggest using Mustang instead.
This list is also a work in progress. Please, let me know if you know other popular, but flawed gems.
Managing processes
- If your projects depends on various external processes use foreman to manage them.
Testing Rails applications
The best approach to implementing new features is probably the BDD approach. You start out by writing some high level feature tests (generally written using Cucumber), then you use these tests to drive out the implementation of the feature. First you write view specs for the feature and use those specs to create the relevant views. Afterwards you create the specs for the controller(s) that will be feeding data to the views and use those specs to implement the controller. Finally you implement the models specs and the models themselves.
Cucumber
-
Tag your pending scenarios with
@wip
(work in progress). These scenarios will not be taken into account and will not be marked as failing. When finishing the work on a pending scenario and implementing the functionality it tests, the tag@wip
should be removed in order to include this scenario in the test suite. -
Setup your default profile to exclude the scenarios tagged with
@javascript
. They are testing using the browser and disabling them is recommended to increase the regular scenarios execution speed. -
Setup a separate profile for the scenarios marked with
@javascript
tag.-
The profiles can be configured in the
cucumber.yml
file.```Ruby # definition of a profile: profile_name: --tags @tag_name ```
-
A profile is run with the command:
``` cucumber -p profile_name ```
-
-
If using fabrication for fixtures replacement, use the predefined fabrication steps
-
Do not use the old
web_steps.rb
step definitions! The web steps were removed from the latest version of Cucumber. Their usage leads to the creation of verbose scenarios that do not properly reflect the application domain. -
When checking for the presence of an element with visible text (link, button, etc.) check for the text, not the element id. This can detect problems with the i18n.
-
Create separate features for different functionality regarding the same kind of objects:
# bad Feature: Articles # ... feature implementation ... # good Feature: Article Editing # ... feature implementation ... Feature: Article Publishing # ... feature implementation ... Feature: Article Search # ... feature implementation ...
-
Each feature has three main components
- Title
- Narrative - a short explanation what the feature is about.
- Acceptance criteria - the set of scenarios each made up of individual steps.
-
The most common format is known as the Connextra format.
In order to [benefit] ... A [stakeholder]... Wants to [feature] ...
This format is the most common but is not required, the narrative can be free text depending on the complexity of the feature.
-
Use Scenario Outlines freely to keep the scenarios DRY.
Scenario Outline: User cannot register with invalid e-mail When I try to register with an email "<email>" Then I should see the error message "<error>" Examples: |email |error | | |The e-mail is required| |invalid email |is not a valid e-mail |
-
The steps for the scenarios are in
.rb
files under thestep_definitions
directory. The naming convention for the steps file is[description]_steps.rb
. The steps can be separated into different files based on different criterias. It is possible to have one steps file for each feature (home_page_steps.rb
). There also can be one steps file for all features for a particular object (articles_steps.rb
). -
Use multiline step arguments to avoid repetition
Scenario: User profile Given I am logged in as a user "John Doe" with an e-mail "[email protected]" When I go to my profile Then I should see the following information: |First name|John | |Last name |Doe | |E-mail |user@test.com| # the step: Then /^I should see the following information:$/ do |table| table.raw.each do |field, value| find_field(field).value.should =~ /#{value}/ end end
-
Use compound steps to keep the scenario DRY
# ... When I subscribe for news from the category "Technical News" # ... # the step: When /^I subscribe for news from the category "([^"]*)"$/ do |category| steps %Q{ When I go to the news categories page And I select the category #{category} And I click the button "Subscribe for this category" And I confirm the subscription } end
-
Always use the Capybara negative matchers instead of should_not with positive, they will retry the match for given timeout allowing you to test ajax actions. See Capybara's README for more explanation
RSpec
-
Use just one expectation per example.
# bad describe ArticlesController do #... describe 'GET new' do it 'assigns new article and renders the new article template' do get :new assigns[:article].should be_a_new Article response.should render_template :new end end # ... end # good describe ArticlesController do #... describe 'GET new' do it 'assigns a new article' do get :new assigns[:article].should be_a_new Article end it 'renders the new article template' do get :new response.should render_template :new end end end
-
Write expectations at a high level, removed from logic and implementation details.
# bad it "calls more_results if i=0" do # ... end # good context "no results are returned by the initial search" do it "attempts to find more results" do # ... end end
-
Avoid incidental state as much as possible.
describe Article do let(:article) { FactoryGirl.create(:article) } let(:another_article) { FactoryGirl.create(:article) } describe "#publish" do # bad it "publishes the article" do article.publish # Creating another shared Article test object above would cause this # test to break Article.count.should == 2 end # good it "publishes the article" do { article.publish }.should change(Article, :count).by(1) end end end
-
Make heavy use of
describe
andcontext
-
Do not use a
context
for a single test -
Try to keep the full spec name (concatentation of the nested descriptions) grammatically correct. These rules offer one way of doing this:
- Top level: use
describe
with a constant name:describe User ...
- 2nd level: use
describe
with a method name:describe "#awesome?"
- Inner blocks: use a
context
that starts withwhen
:context "when user is unsubscribed"
- Example describes the expectation:
it "is false"
, notit "should be false"
- Full spec name: "User#awesome? when user is unsubscribed is false"
- Top level: use
-
Name the
describe
blocks as follows:-
use "description" for non-methods
-
use pound "#method" for instance methods
-
use dot ".method" for class methods
class Article def summary #... end def self.latest #... end end # the spec... describe Article describe '#summary' #... end describe '.latest' #... end end
-
-
Use Factory Girl to create test objects.
-
Make heavy use of mocks and stubs
# mocking a model article = mock_model(Article) # stubbing a method Article.stub(:find).with(article.id).and_return(article)
-
When mocking a model, use the
as_null_object
method. It tells the output to listen only for messages we expect and ignore any other messages.article = mock_model(Article).as_null_object
-
Use
let
blocks instead ofbefore(:each)
blocks to create data for the spec examples.let
blocks get lazily evaluated.# use this: let(:article) { Fabricate(:article) } # ... instead of this: before(:each) { @article = Fabricate(:article) }
-
Use
subject
when possibledescribe Article do subject { Fabricate(:article) } it 'is not published on creation' do subject.should_not be_published end end
-
Use
specify
if possible. It is a synonym ofit
but is more readable when there is no docstring.# bad describe Article do before { @article = Fabricate(:article) } it 'is not published on creation' do @article.should_not be_published end end # good describe Article do let(:article) { Fabricate(:article) } specify { article.should_not be_published } end
-
Use
its
when possible# bad describe Article do subject { Fabricate(:article) } it 'has the current date as creation date' do subject.creation_date.should == Date.today end end # good describe Article do subject { Fabricate(:article) } its(:creation_date) { should == Date.today } end
Views
-
The directory structure of the view specs
spec/views
matches the one inapp/views
. For example the specs for the views inapp/views/users
are placed inspec/views/users
. -
The naming convention for the view specs is adding
_spec.rb
to the view name, for example the view_form.html.haml
has a corresponding spec_form.html.haml_spec.rb
. -
spec_helper.rb
need to be required in each view spec file. -
The outer
describe
block uses the path to the view without theapp/views
part. This is used by therender
method when it is called without arguments.# spec/views/articles/new.html.haml_spec.rb require 'spec_helper' describe 'articles/new.html.haml' do # ... end
-
Always mock the models in the view specs. The purpose of the view is only to display information.
-
The method
assign
supplies the instance variables which the view uses and are supplied by the controller.# spec/views/articles/edit.html.haml_spec.rb describe 'articles/edit.html.haml' do it 'renders the form for a new article creation' do assign( :article, mock_model(Article).as_new_record.as_null_object ) render rendered.should have_selector('form', method: 'post', action: articles_path ) do |form| form.should have_selector('input', type: 'submit') end end
-
Prefer the capybara negative selectors over should_not with the positive.
# bad page.should_not have_selector('input', type: 'submit') page.should_not have_xpath('tr') # good page.should have_no_selector('input', type: 'submit') page.should have_no_xpath('tr')
-
When a view uses helper methods, these methods need to be stubbed. Stubbing the helper methods is done on the
template
object:# app/helpers/articles_helper.rb class ArticlesHelper def formatted_date(date) # ... end end # app/views/articles/show.html.haml = "Published at: #{formatted_date(@article.published_at)}" # spec/views/articles/show.html.haml_spec.rb describe 'articles/show.html.haml' do it 'displays the formatted date of article publishing' article = mock_model(Article, published_at: Date.new(2012, 01, 01)) assign(:article, article) template.stub(:formatted_date).with(article.published_at).and_return('01.01.2012') render rendered.should have_content('Published at: 01.01.2012') end end
-
The helpers specs are separated from the view specs in the
spec/helpers
directory.
Controllers
-
Mock the models and stub their methods. Testing the controller should not depend on the model creation.
-
Test only the behaviour the controller should be responsible about:
-
Execution of particular methods
-
Data returned from the action - assigns, etc.
-
Result from the action - template render, redirect, etc.
```Ruby # Example of a commonly used controller spec # spec/controllers/articles_controller_spec.rb # We are interested only in the actions the controller should perform # So we are mocking the model creation and stubbing its methods # And we concentrate only on the things the controller should do describe ArticlesController do # The model will be used in the specs for all methods of the controller let(:article) { mock_model(Article) } describe 'POST create' do before { Article.stub(:new).and_return(article) } it 'creates a new article with the given attributes' do Article.should_receive(:new).with(title: 'The New Article Title').and_return(article) post :create, message: { title: 'The New Article Title' } end it 'saves the article' do article.should_receive(:save) post :create end it 'redirects to the Articles index' do article.stub(:save) post :create response.should redirect_to(action: 'index') end end end ```
-
-
Use context when the controller action has different behaviour depending on the received params.
# A classic example for use of contexts in a controller spec is creation or update when the object saves successfully or not. describe ArticlesController do let(:article) { mock_model(Article) } describe 'POST create' do before { Article.stub(:new).and_return(article) } it 'creates a new article with the given attributes' do Article.should_receive(:new).with(title: 'The New Article Title').and_return(article) post :create, article: { title: 'The New Article Title' } end it 'saves the article' do article.should_receive(:save) post :create end context 'when the article saves successfully' do before { article.stub(:save).and_return(true) } it 'sets a flash[:notice] message' do post :create flash[:notice].should eq('The article was saved successfully.') end it 'redirects to the Articles index' do post :create response.should redirect_to(action: 'index') end end context 'when the article fails to save' do before { article.stub(:save).and_return(false) } it 'assigns @article' do post :create assigns[:article].should be_eql(article) end it 're-renders the "new" template' do post :create response.should render_template('new') end end end end
Models
-
Do not mock the models in their own specs.
-
Use FactoryGirl to make real objects.
-
It is acceptable to mock other models or child objects.
-
Create the model for all examples in the spec to avoid duplication.
describe Article let(:article) { Fabricate(:article) } end
-
Add an example ensuring that the factory created model is valid.
describe Article it 'is valid with valid attributes' do article.should be_valid end end
-
When testing validations, use
have(x).errors_on
to specify the attibute which should be validated. Usingbe_valid
does not guarantee that the problem is in the intended attribute.# bad describe '#title' it 'is required' do article.title = nil article.should_not be_valid end end # prefered describe '#title' it 'is required' do article.title = nil article.should have(1).error_on(:title) end end
-
Add a separate
describe
for each attribute which has validations.describe Article describe '#title' it 'is required' do article.title = nil article.should have(1).error_on(:title) end end end
-
When testing uniqueness of a model attribute, name the other object
another_object
.describe Article describe '#title' it 'is unique' do another_article = Fabricate.build(:article, title: article.title) article.should have(1).error_on(:title) end end end
Mailers
- The model in the mailer spec should be mocked. The mailer should not depend on the model creation.
- The mailer spec should verify that:
-
the subject is correct
-
the receiver e-mail is correct
-
the e-mail is sent to the right e-mail address
-
the e-mail contains the required information
describe SubscriberMailer let(:subscriber) { mock_model(Subscription, email: '[email protected]', name: 'John Doe') } describe 'successful registration email' subject { SubscriptionMailer.successful_registration_email(subscriber) } its(:subject) { should == 'Successful Registration!' } its(:from) { should == ['info@your_site.com'] } its(:to) { should == [subscriber.email] } it 'contains the subscriber name' do subject.body.encoded.should match(subscriber.name) end end end
-
Uploaders
-
What we can test about an uploader is whether the images are resized correctly. Here is a sample spec of a carrierwave image uploader:
# rspec/uploaders/person_avatar_uploader_spec.rb require 'spec_helper' require 'carrierwave/test/matchers' describe PersonAvatarUploader do include CarrierWave::Test::Matchers # Enable images processing before executing the examples before(:all) do UserAvatarUploader.enable_processing = true end # Create a new uploader. The model is mocked as the uploading and resizing images does not depend on the model creation. before(:each) do @uploader = PersonAvatarUploader.new(mock_model(Person).as_null_object) @uploader.store!(File.open(path_to_file)) end # Disable images processing after executing the examples after(:all) do UserAvatarUploader.enable_processing = false end # Testing whether image is no larger than given dimensions context 'the default version' do it 'scales down an image to be no larger than 256 by 256 pixels' do @uploader.should be_no_larger_than(256, 256) end end # Testing whether image has the exact dimensions context 'the thumb version' do it 'scales down an image to be exactly 64 by 64 pixels' do @uploader.thumb.should have_dimensions(64, 64) end end end
Above all else
Follow your
Further Reading
There are a few excellent resources on Rails style, that you should consider if you have time to spare:
Contributing
Nothing written in this guide is set in stone. It's my desire to work together with everyone interested in Rails coding style, so that we could ultimately create a resource that will be beneficial to the entire Ruby community.
Feel free to open tickets or send pull requests with improvements. Thanks in advance for your help!
Spread the Word
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