RSpec Rails

rspec-rails brings the RSpec testing framework to Ruby on Rails as a drop-in alternative to its default testing framework, Minitest.

In RSpec, tests are not just scripts that verify your application code. They’re also specifications (or specs, for short): detailed explanations of how the application is supposed to behave, expressed in plain English.

According to RSpec Rails new versioning strategy use:

• rspec-rails 6.x for Rails 6.1 or 7.x.
• rspec-rails 5.x for Rails 5.2 or 6.x.
• rspec-rails 4.x for Rails from 5.x or 6.x.
• rspec-rails 3.x for Rails earlier than 5.0.
• rspec-rails 1.x for Rails 2.x.

Installation

IMPORTANT This README / branch refers to the 6.1.x stable release series, only bugfixes from this series will be added here. See the main branch on Github if you want or require the latest unstable features.

1. Add rspec-rails to both the :development and :test groups of your app’s Gemfile:

   # Run against this stable release
   group :development, :test do
     gem 'rspec-rails', '~> 6.1.0'
   end
   
   # Or, run against the main branch
   # (requires main-branch versions of all related RSpec libraries)
   group :development, :test do
     %w[rspec-core rspec-expectations rspec-mocks rspec-rails rspec-support].each do |lib|
       gem lib, git: "https://github.com/rspec/#{lib}.git", branch: 'main'
     end
   end

   (Adding it to the :development group is not strictly necessary, but without it, generators and rake tasks must be preceded by RAILS_ENV=test.)

2. Then, in your project directory:

   # Download and install
   $ bundle install
   
   # Generate boilerplate configuration files
   # (check the comments in each generated file for more information)
   $ rails generate rspec:install
         create  .rspec
         create  spec
         create  spec/spec_helper.rb
         create  spec/rails_helper.rb

Upgrading

If your project is already using an older version of rspec-rails, upgrade to the latest version with:

$ bundle update rspec-rails

RSpec follows semantic versioning, which means that “major version” upgrades (e.g., 2.x → 3.x) come with breaking changes. If you’re upgrading from version 2.x or below, read the rspec-rails upgrade notes to find out what to watch out for.

Be sure to check the general RSpec upgrade notes as well.

Usage

Creating boilerplate specs with rails generate

# RSpec hooks into built-in generators
$ rails generate model user
      invoke  active_record
      create    db/migrate/20181017040312_create_users.rb
      create    app/models/user.rb
      invoke    rspec
      create      spec/models/user_spec.rb

# RSpec also provides its own spec file generators
$ rails generate rspec:model user
      create  spec/models/user_spec.rb

# List all RSpec generators
$ rails generate --help | grep rspec

Running specs

# Default: Run all spec files (i.e., those matching spec/**/*_spec.rb)
$ bundle exec rspec

# Run all spec files in a single directory (recursively)
$ bundle exec rspec spec/models

# Run a single spec file
$ bundle exec rspec spec/controllers/accounts_controller_spec.rb

# Run a single example from a spec file (by line number)
$ bundle exec rspec spec/controllers/accounts_controller_spec.rb:8

# See all options for running specs
$ bundle exec rspec --help

Optional: If bundle exec rspec is too verbose for you, you can generate a binstub at bin/rspec and use that instead:

$ bundle binstubs rspec-core

RSpec DSL Basics (or, how do I write a spec?)

In RSpec, application behavior is described first in (almost) plain English, then again in test code, like so:

RSpec.describe 'Post' do           #
  context 'before publication' do  # (almost) plain English
    it 'cannot have comments' do   #
      expect { Post.create.comments.create! }.to raise_error(ActiveRecord::RecordInvalid)  # test code
    end
  end
end

Running rspec will execute this test code, and then use the plain-English descriptions to generate a report of where the application conforms to (or fails to meet) the spec:

$ rspec --format documentation spec/models/post_spec.rb

Post
  before publication
    cannot have comments

Failures:

  1) Post before publication cannot have comments
     Failure/Error: expect { Post.create.comments.create! }.to raise_error(ActiveRecord::RecordInvalid)
       expected ActiveRecord::RecordInvalid but nothing was raised
     # ./spec/models/post.rb:4:in `block (3 levels) in <top (required)>'

Finished in 0.00527 seconds (files took 0.29657 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/models/post_spec.rb:3 # Post before publication cannot have comments

For an in-depth look at the RSpec DSL, including lots of examples, read the official Cucumber documentation for RSpec Core.

Helpful Rails Matchers

In RSpec, assertions are called expectations, and every expectation is built around a matcher. When you expect(a).to eq(b), you’re using the eq matcher.

In addition to the matchers that come standard in RSpec, here are some extras that make it easier to test the various parts of a Rails system:

RSpec matcher	Delegates to	Available in	Notes
be_a_new		all	primarily intended for controller specs
render_template	assert_template	request / controller / view	use with expect(response).to
redirect_to	assert_redirect	request / controller	use with expect(response).to
route_to	assert_recognizes	routing / controller	use with expect(...).to route_to
be_routable		routing / controller	use with expect(...).not_to be_routable
have_http_status		request / controller / feature
match_array		all	for comparing arrays of ActiveRecord objects
have_been_enqueued		all	requires config: ActiveJob::Base.queue_adapter = :test
have_enqueued_job		all	requires config: ActiveJob::Base.queue_adapter = :test

Follow the links above for examples of how each matcher is used.

What else does RSpec Rails add?

For a comprehensive look at RSpec Rails’ features, read the official Cucumber documentation.

What tests should I write?

RSpec Rails defines ten different types of specs for testing different parts of a typical Rails application. Each one inherits from one of Rails’ built-in TestCase classes, meaning the helper methods provided by default in Rails tests are available in RSpec, as well.

Spec type	Corresponding Rails test class
model
controller	ActionController::TestCase
mailer	ActionMailer::TestCase
job
view	ActionView::TestCase
routing
helper	ActionView::TestCase
request	ActionDispatch::IntegrationTest
feature
system	ActionDispatch::SystemTestCase

Follow the links above to see examples of each spec type, or for official Rails API documentation on the given TestCase class.

Note: This is not a checklist.

Ask a hundred developers how to test an application, and you’ll get a hundred different answers.

RSpec Rails provides thoughtfully selected features to encourage good testing practices, but there’s no “right” way to do it. Ultimately, it’s up to you to decide how your test suite will be composed.

When creating a spec file, assign it a type in the top-level describe block, like so:

# spec/models/user_spec.rb

RSpec.describe User, type: :model do
...

System specs, feature specs, request specs–what’s the difference?

RSpec Rails provides some end-to-end (entire application) testing capability to specify the interaction with the client.

System specs

Also called acceptance tests, browser tests, or end-to-end tests, system specs test the application from the perspective of a human client. The test code walks through a user’s browser interactions,

• visit '/login'
• fill_in 'Name', with: 'jdoe'

and the expectations revolve around page content.

• expect(page).to have_text('Welcome')

Because system specs are a wrapper around Rails’ built-in SystemTestCase, they’re only available on Rails 5.1+. (Feature specs serve the same purpose, but without this dependency.)

Feature specs

Before Rails introduced system testing facilities, feature specs were the only spec type for end-to-end testing. While the RSpec team now officially recommends system specs instead, feature specs are still fully supported, look basically identical, and work on older versions of Rails.

On the other hand, feature specs require non-trivial configuration to get some important features working, like JavaScript testing or making sure each test runs with a fresh DB state. With system specs, this configuration is provided out-of-the-box.

Like system specs, feature specs require the Capybara gem. Rails 5.1+ includes it by default as part of system tests, but if you don’t have the luxury of upgrading, be sure to add it to the :test group of your Gemfile first:

group :test do
  gem "capybara"
end

Request specs

Request specs are for testing the application from the perspective of a machine client. They begin with an HTTP request and end with the HTTP response, so they’re faster than feature specs, but do not examine your app’s UI or JavaScript.

Request specs provide a high-level alternative to controller specs. In fact, as of RSpec 3.5, both the Rails and RSpec teams discourage directly testing controllers in favor of functional tests like request specs.

When writing them, try to answer the question, “For a given HTTP request (verb + path + parameters), what HTTP response should the application return?”

See Also

RSpec base libraries

• https://github.com/rspec/rspec
• https://github.com/rspec/rspec-core
• https://github.com/rspec/rspec-expectations
• https://github.com/rspec/rspec-mocks

Recommended third-party extensions

• FactoryBot

• Capybara (Included by default in Rails 5.1+. Note that additional configuration is required to use the Capybara DSL anywhere other than system specs and feature specs.)