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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 community-driven 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. In my mind I'm totally certain that RSpec is superior to Test::Unit, Sass is superior to CSS and Haml (Slim) is superior to Erb. So don't expect to find any Test::Unit, CSS or Erb advice in here.

Some of the advice here is applicable only to Rails 3.1+.

You can generate a PDF or an HTML copy of this guide using Transmuter.

Translations of the guide are available in the following languages:

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 )
      ```
      
  • Keep configuration that's applicable to all environments in the config/application.rb file.

  • Create an additional staging environment that closely resembles the production one.

Routing

  • When you need to add more actions to a RESTful resource (do you really need them at all?) use member and collection 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.

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 to has_and_belongs_to_many. Using has_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 (unlike update_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 the id of the record as a String. It could be overridden to include another human-readable attribute.

      ```Ruby
      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. The id of the object needs to be at the beginning so that it can be found by the find 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 its id.

      ```Ruby
      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.
      

ActiveResource

  • 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 format and use it in the class. The custom format should implement the following four methods: extension, mime_type, encode and decode.

    module ActiveResource
      module Formats
        module Extend
          module CSVFormat
            extend self
    
            def extension
              'csv'
            end
    
            def mime_type
              'text/csv'
            end
    
            def encode(hash, options = nil)
              # Encode the data in the new format and return it
            end
    
            def decode(csv)
              # Decode the data from the new format and return it
            end
          end
        end
      end
    end
    
    class User < ActiveResource::Base
      self.format = ActiveResource::Formats::Extend::CSVFormat
    
      ...
    end
  • If the request should be sent without extension, override the element_path and collection_path methods of ActiveResource::Base and remove the extension part.

    class User < ActiveResource::Base
      ...
    
      def self.collection_path(prefix_options = {}, query_options = nil)
        prefix_options, query_options = split_options(prefix_options) if query_options.nil?
        "#{prefix(prefix_options)}#{collection_name}#{query_string(query_options)}"
      end
    
      def self.element_path(id, prefix_options = {}, query_options = nil)
        prefix_options, query_options = split_options(prefix_options) if query_options.nil?
        "#{prefix(prefix_options)}#{collection_name}/#{URI.parser.escape id.to_s}#{query_string(query_options)}"
      end
    end

    These methods can be overridden also if any other modifications of the URL are needed.

Migrations

  • Keep the schema.rb under version control.

  • Use rake db:schema:load instead of rake 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 of up and down 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 your application.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" and User.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 folder views.

    • 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 of I18n.translate and I18n.l instead of I18n.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 template app/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.
  • Use lib/assets for your own libraries, that doesn’t really fit into the scope of the application.
  • Third party code such as jQuery or bootstrap should be placed in vendor/assets.
  • When possible, use 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 a darwin group in the Gemfile, and all Linux specific gems to a linux 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 a bundle 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.
  • better_errors - Better Errors replaces the standard Rails error page with a much better and more useful error page. It is also usable outside of Rails in any Rack app as Rack middleware.
  • bullet - The Bullet gem is designed to help you increase your application’s performance by reducing the number of queries it makes. It will watch your queries while you develop your application and notify you when you should add eager loading (N+1 queries), when you’re using eager loading that isn’t necessary and when you should use counter cache.
  • cancan - CanCan is an authorization gem that lets you restrict users access to resources. All permissions are defined in a single file (ability.rb) and convenient methods for checking and ensuring permissions are available throughout the application.
  • 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.
  • ffaker - 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.
  • globalize3 - Globalize3 is the successor of Globalize for Rails and is targeted at ActiveRecord version 3.x. It is compatible with and builds on the new I18n API in Ruby on Rails and adds model translations to ActiveRecord.
  • 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.
  • haml-rails - haml-rails provides Rails integration for Haml.
  • haml - HAML is a concise templating language, considered by many (including yours truly) to be far superior to Erb.
  • 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!
  • slim - Slim is a concise templating language, considered by many far superior to HAML (not to mention Erb). The only thing stopping me from using Slim massively is the lack of good support in major editors/IDEs. Its performance is phenomenal.
  • 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.

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 node.js 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 the step_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
  • Make heavy use of describe and context

  • 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 do
        describe '#summary' do
          #...
        end
      
        describe '.latest' do
          #...
        end
      end
  • Use fabricators 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 of before(: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 possible

    describe 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 of it 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
  • Use shared_examples if you want to create a spec group that can be shared by many other tests.

    # bad
     describe Array do
       subject { Array.new [7, 2, 4] }
     
       context "initialized with 3 items" do
         its(:size) { should eq(3) }
       end
     end
     
     describe Set do
       subject { Set.new [7, 2, 4] }
     
       context "initialized with 3 items" do
         its(:size) { should eq(3) }
       end
     end
     
    #good
     shared_examples "a collection" do
       subject { described_class.new([7, 2, 4]) } 
     
       context "initialized with 3 items" do
         its(:size) { should eq(3) }
       end
     end
     
     describe Array do
       it_behaves_like "a collection"
     end
     
     describe Set do
       it_behaves_like "a collection"
     end

Views

  • The directory structure of the view specs spec/views matches the one in app/views. For example the specs for the views in app/views/users are placed in spec/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 the app/views part. This is used by the render 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' do
        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 fabrication 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 do
      let(:article) { Fabricate(:article) }
    end
  • Add an example ensuring that the fabricated model is valid.

    describe Article do
      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. Using be_valid does not guarantee that the problem is in the intended attribute.

    # bad
    describe '#title' do
      it 'is required' do
        article.title = nil
        article.should_not be_valid
      end
    end
    
    # prefered
    describe '#title' do
      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 do
      describe '#title' do
        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 do
      describe '#title' do
        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 do
        let(:subscriber) { mock_model(Subscription, email: '[email protected]', name: 'John Doe') }
      
        describe 'successful registration email' do
          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

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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