rubocop/rspec-style-guide

= RSpec Style Guide :idprefix: :idseparator: - :sectanchors: :sectlinks: :toc: preamble :toclevels: 1 ifndef::backend-pdf[] :toc-title: pass:[

Table of Contents

== Introduction

[quote, Officer Alex J. Murphy / RoboCop]

Role models are important.

ifdef::env-github[] TIP: You can find a beautiful version of this guide with much improved navigation at https://rspec.rubystyle.guide. endif::[]

This RSpec style guide outlines the recommended best practices for real-world programmers to write code that can be maintained by other real-world programmers.

https://github.com/rubocop/rubocop[RuboCop], a static code analyzer (linter) and formatter, has a https://github.com/rubocop/rubocop-rspec[`rubocop-rspec`] extension, provides a way to enforce the rules outlined in this guide.

NOTE: This guide assumes you are using RSpec 3 or later.

You can generate a PDF copy of this guide using https://asciidoctor.org/docs/asciidoctor-pdf/[AsciiDoctor PDF], and an HTML copy https://asciidoctor.org/docs/convert-documents/#converting-a-document-to-html[with] https://asciidoctor.org/#installation[AsciiDoctor] using the following commands:

[source,shell]

Generates README.pdf

asciidoctor-pdf -a allow-uri-read README.adoc

Generates README.html

asciidoctor README.adoc

[TIP]

Install the rouge gem to get nice syntax highlighting in the generated document.

[source,shell]

gem install rouge

====

== How to Read This Guide

The guide is separated into sections based on the different pieces of an entire spec file. There was an attempt to omit all obvious information, if anything is unclear, feel free to open an issue asking for further clarity.

== A Living Document

Per the comment above, this guide is a work in progress - some rules are simply lacking thorough examples, but some things in the RSpec world change week by week or month by month. With that said, as the standard changes this guide is meant to be able to change with it.

== Layout

=== Empty Lines inside Example Group[[empty-lines-after-describe]]

Do not leave empty lines after feature, context or describe descriptions. It doesn't make the code more readable and lowers the value of logical chunks.

[source,ruby]

bad

describe Article do

describe '#summary' do

context 'when there is a summary' do

  it 'returns the summary' do
    # ...
  end
end

end end

good

describe Article do describe '#summary' do context 'when there is a summary' do it 'returns the summary' do # ... end end end end

=== Empty Line between Example Groups [[empty-lines-between-describes]]

Leave one empty line between feature, context or describe blocks. Do not leave empty line after the last such block in a group.

[source,ruby]

bad

describe Article do describe '#summary' do context 'when there is a summary' do # ... end context 'when there is no summary' do # ... end

end describe '#comments' do # ... end end

good

describe Article do describe '#summary' do context 'when there is a summary' do # ... end

context 'when there is no summary' do
  # ...
end

end

describe '#comments' do # ... end end

=== Empty Line After let[[empty-lines-after-let]]

Leave one empty line after let, subject, and before/after blocks.

[source,ruby]

bad

describe Article do subject { FactoryBot.create(:some_article) } describe '#summary' do # ... end end

good

describe Article do subject { FactoryBot.create(:some_article) }

describe '#summary' do # ... end end

=== Let Grouping

Only group let, subject blocks and separate them from before/after blocks. It makes the code much more readable.

[source,ruby]

bad

describe Article do subject { FactoryBot.create(:some_article) } let(:user) { FactoryBot.create(:user) } before do # ... end after do # ... end describe '#summary' do # ... end end

good

describe Article do subject { FactoryBot.create(:some_article) } let(:user) { FactoryBot.create(:user) }

before do # ... end

after do # ... end

describe '#summary' do # ... end end

=== Empty Lines around Examples[[empty-lines-around-it]]

Leave one empty line around it/specify blocks. This helps to separate the expectations from their conditional logic (contexts for instance).

[source,ruby]

bad

describe '#summary' do let(:item) { double('something') }

it 'returns the summary' do # ... end it 'does something else' do # ... end it 'does another thing' do # ... end end

good

describe '#summary' do let(:item) { double('something') }

it 'returns the summary' do # ... end

it 'does something else' do # ... end

it 'does another thing' do # ... end end

== Example Group Structure

=== Leading subject

When subject is used, it should be the first declaration in the example group.

[source,ruby]

bad

describe Article do before do # ... end

let(:user) { FactoryBot.create(:user) } subject { FactoryBot.create(:some_article) }

describe '#summary' do # ... end end

good

describe Article do subject { FactoryBot.create(:some_article) } let(:user) { FactoryBot.create(:user) }

before do # ... end

describe '#summary' do # ... end end

=== Declaring subject, let!/let and before/after hooks

When declaring subject, let!/let and before/after hooks they should be in the following order:

• subject
• let!/let
• before/after

[source,ruby]

bad

describe Article do before do # ... end

after do # ... end

let(:user) { FactoryBot.create(:user) } subject { FactoryBot.create(:some_article) }

describe '#summary' do # ... end end

good

describe Article do subject { FactoryBot.create(:some_article) } let(:user) { FactoryBot.create(:user) }

before do # ... end

after do # ... end

describe '#summary' do # ... end end

=== Use Contexts

Use contexts to make the tests clear, well organized, and easy to read.

[source,ruby]

bad

it 'has 200 status code if logged in' do expect(response).to respond_with 200 end

it 'has 401 status code if not logged in' do expect(response).to respond_with 401 end

good

context 'when logged in' do it { is_expected.to respond_with 200 } end

context 'when logged out' do it { is_expected.to respond_with 401 } end

=== Context Cases

context blocks should pretty much always have an opposite negative case. It is a code smell if there is a single context (without a matching negative case), and this code needs refactoring, or may have no purpose.

[source,ruby]

bad - needs refactoring

describe '#attributes' do context 'the returned hash' do it 'includes the display name' do # ... end

it 'includes the creation time' do
  # ...
end

end end

bad - the negative case needs to be tested, but isn't

describe '#attributes' do context 'when display name is present' do before do article.display_name = 'something' end

it 'includes the display name' do
  # ...
end

end end

good

describe '#attributes' do subject(:attributes) { article.attributes } let(:article) { FactoryBot.create(:article) }

context 'when display name is present' do before do article.display_name = 'something' end

it { is_expected.to include(display_name: article.display_name) }

end

context 'when display name is not present' do before do article.display_name = nil end

it { is_expected.not_to include(:display_name) }

end end

=== let Blocks

Use let and let! for data that is used across several examples in an example group. Use let! to define variables even if they are not referenced in some of the examples, e.g. when testing balancing negative cases. Do not overuse lets for primitive data, find the balance between frequency of use and complexity of the definition.

[source,ruby]

bad

it 'finds shortest path' do tree = Tree.new(1 => 2, 2 => 3, 2 => 6, 3 => 4, 4 => 5, 5 => 6) expect(dijkstra.shortest_path(tree, from: 1, to: 6)).to eq([1, 2, 6]) end

it 'finds longest path' do tree = Tree.new(1 => 2, 2 => 3, 2 => 6, 3 => 4, 4 => 5, 5 => 6) expect(dijkstra.longest_path(tree, from: 1, to: 6)).to eq([1, 2, 3, 4, 5, 6]) end

good

let(:tree) { Tree.new(1 => 2, 2 => 3, 2 => 6, 3 => 4, 4 => 5, 5 => 6) }

it 'finds shortest path' do expect(dijkstra.shortest_path(tree, from: 1, to: 6)).to eq([1, 2, 6]) end

it 'finds longest path' do expect(dijkstra.longest_path(tree, from: 1, to: 6)).to eq([1, 2, 3, 4, 5, 6]) end

=== Instance Variables

Use let definitions instead of instance variables.

[source,ruby]

bad

before { @name = 'John Wayne' }

it 'reverses a name' do expect(reverser.reverse(@name)).to eq('enyaW nhoJ') end

good

let(:name) { 'John Wayne' }

it 'reverses a name' do expect(reverser.reverse(name)).to eq('enyaW nhoJ') end

=== Shared Examples

Use shared examples to reduce code duplication.

[source,ruby]

bad

describe 'GET /articles' do let(:article) { FactoryBot.create(:article, owner: owner) }

before { page.driver.get '/articles' }

context 'when user is the owner' do let(:user) { owner }

it 'shows all owned articles' do
  expect(page.status_code).to be(200)
  contains_resource resource
end

end

context 'when user is an admin' do let(:user) { FactoryBot.create(:user, :admin) }

it 'shows all resources' do
  expect(page.status_code).to be(200)
  contains_resource resource
end

end end

good

describe 'GET /articles' do let(:article) { FactoryBot.create(:article, owner: owner) }

before { page.driver.get '/articles' }

shared_examples 'shows articles' do it 'shows all related articles' do expect(page.status_code).to be(200) contains_resource resource end end

context 'when user is the owner' do let(:user) { owner }

include_examples 'shows articles'

end

context 'when user is an admin' do let(:user) { FactoryBot.create(:user, :admin) }

include_examples 'shows articles'

end end

good

describe 'GET /devices' do let(:resource) { FactoryBot.create(:device, created_from: user) }

it_behaves_like 'a listable resource' it_behaves_like 'a paginable resource' it_behaves_like 'a searchable resource' it_behaves_like 'a filterable list' end

=== Redundant before(:each)

Don't specify :each/:example scope for before/after/around blocks, as it is the default. Prefer :example when explicitly indicating the scope.

[source,ruby]

bad

describe '#summary' do before(:example) do # ... end

...

end

good

describe '#summary' do before do # ... end

...

end

=== Ambiguous Hook Scope

Use :context instead of the ambiguous :all scope in before/after hooks.

[source,ruby]

bad

describe '#summary' do before(:all) do # ... end

...

end

good

describe '#summary' do before(:context) do # ... end

...

end

=== Avoid Hooks with :context Scope

Avoid using before/after with :context scope. Beware of the state leakage between the examples.

== Example Structure

=== Expectation per Example[[one-expectation]]

For examples two styles are considered acceptable. The first variant is separate example for each expectation, which comes with a cost of repeated context initialization. The second variant is multiple expectations per example with aggregate_failures tag set for a group or example. Use your best judgement in each case, and apply your strategy consistently.

[source,ruby]

good - one expectation per example

describe ArticlesController do #...

describe 'GET new' do it 'assigns a new article' do get :new expect(assigns[:article]).to be_a(Article) end

it 'renders the new article template' do
  get :new
  expect(response).to render_template :new
end

end end

good - multiple expectations with aggregated failures

describe ArticlesController do #...

describe 'GET new', :aggregate_failures do it 'assigns new article and renders the new article template' do get :new expect(assigns[:article]).to be_a(Article) expect(response).to render_template :new end end

...

end

=== Subject

When several tests relate to the same subject, use subject to reduce repetition.

[source,ruby]

bad

it { expect(hero.equipment).to be_heavy } it { expect(hero.equipment).to include 'sword' }

good

subject(:equipment) { hero.equipment }

it { expect(equipment).to be_heavy } it { expect(equipment).to include 'sword' }

=== Named Subject [[use-subject]]

Use named subject when possible. Only use anonymous subject declaration when you don't reference it in any tests, e.g. when is_expected is used.

[source,ruby]

bad

describe Article do subject { FactoryBot.create(:article) }

it 'is not published on creation' do expect(subject).not_to be_published end end

good

describe Article do subject { FactoryBot.create(:article) }

it 'is not published on creation' do is_expected.not_to be_published end end

even better

describe Article do subject(:article) { FactoryBot.create(:article) }

it 'is not published on creation' do expect(article).not_to be_published end end

=== Subject Naming in Context

When you reassign subject with different attributes in different contexts, give different names to the subject, so it's easier to see what the actual subject represents.

[source,ruby]

bad

describe Article do context 'when there is an author' do subject(:article) { FactoryBot.create(:article, author: user) }

it 'shows other articles by the same author' do
  expect(article.related_stories).to include(story1, story2)
end

end

context 'when the author is anonymous' do subject(:article) { FactoryBot.create(:article, author: nil) }

it 'matches stories by title' do
  expect(article.related_stories).to include(story3, story4)
end

end end

good

describe Article do context 'when article has an author' do subject(:article) { FactoryBot.create(:article, author: user) }

it 'shows other articles by the same author' do
  expect(article.related_stories).to include(story1, story2)
end

end

context 'when the author is anonymous' do subject(:guest_article) { FactoryBot.create(:article, author: nil) }

it 'matches stories by title' do
  expect(guest_article.related_stories).to include(story3, story4)
end

end end

=== Don't Stub Subject

Don't stub methods of the object under test, it's a code smell and often indicates a bad design of the object itself.

[source,ruby]

bad

describe 'Article' do subject(:article) { Article.new }

it 'indicates that the author is unknown' do allow(article).to receive(:author).and_return(nil) expect(article.description).to include('by an unknown author') end end

good - with correct subject initialization

describe 'Article' do subject(:article) { Article.new(author: nil) }

it 'indicates that the author is unknown' do expect(article.description).to include('by an unknown author') end end

good - with better object design

describe 'Article' do subject(:presenter) { ArticlePresenter.new(article) } let(:article) { Article.new }

it 'indicates that the author is unknown' do allow(article).to receive(:author).and_return(nil) expect(presenter.description).to include('by an unknown author') end end

=== it and specify

Use specify if the example doesn't have a description, use it for examples with descriptions. An exception is one-line example, where it is preferable. specify is also useful when the docstring does not read well off of it.

[source,ruby]

bad

it do

...

end

specify 'it sends an email' do

...

end

specify { is_expected.to be_truthy }

it '#do_something is deprecated' do ... end

good

specify do

...

end

it 'sends an email' do

...

end

it { is_expected.to be_truthy }

specify '#do_something is deprecated' do ... end

=== it in Iterators

Do not write iterators to generate tests. When another developer adds a feature to one of the items in the iteration, they must then break it out into a separate test - they are forced to edit code that has nothing to do with their pull request.

[source,ruby]

bad

[:new, :show, :index].each do |action| it 'returns 200' do get action expect(response).to be_ok end end

good - more verbose, but better for the future development

describe 'GET new' do it 'returns 200' do get :new expect(response).to be_ok end end

describe 'GET show' do it 'returns 200' do get :show expect(response).to be_ok end end

describe 'GET index' do it 'returns 200' do get :index expect(response).to be_ok end end

=== Incidental State

Avoid incidental state as much as possible.

[source,ruby]

bad

it 'publishes the article' do article.publish

Creating another shared Article test object above would cause this

test to break

expect(Article.count).to eq(2) end

good

it 'publishes the article' do expect { article.publish }.to change(Article, :count).by(1) end

=== DRY

Be careful not to focus on being 'DRY' by moving repeated expectations into a shared environment too early, as this can lead to brittle tests that rely too much on one another.

In general, it is best to start with doing everything directly in your it blocks even if it is duplication and then refactor your tests after you have them working to be a little more DRY. However, keep in mind that duplication in test suites is NOT frowned upon, in fact it is preferred if it provides easier understanding and reading of a test.

=== Factories

Use https://github.com/thoughtbot/factory_bot[Factory Bot] to create test data in integration tests. You should very rarely have to use ModelName.create within an integration spec. Do not use fixtures as they are not nearly as maintainable as factories.

[source,ruby]

bad

subject(:article) do Article.create( title: 'Piccolina', author: 'John Archer', published_at: '17 August 2172', approved: true ) end

good

subject(:article) { FactoryBot.create(:article) }

NOTE: When talking about unit tests the best practice would be to use neither fixtures nor factories. Put as much of your domain logic in libraries that can be tested without needing complex, time consuming setup with either factories or fixtures.

=== Needed Data

Do not load more data than needed to test your code.

[source,ruby]

good

RSpec.describe User do describe ".top" do subject { described_class.top(2) }

before { FactoryBot.create_list(:user, 3) }

it { is_expected.to have(2).items }

end end

=== Doubles

Prefer using verifying doubles over normal doubles.

Verifying doubles are a stricter alternative to normal doubles that provide guarantees, e.g. a failure will be triggered if an invalid method is being stubbed or a method is called with an invalid number of arguments.

In general, use doubles with more isolated/behavioral tests rather than with integration tests.

NOTE: There is no justification for turning verify_partial_doubles configuration option off. That will significantly reduce the confidence in partial doubles.

[source,ruby]

good - verifying instance double

article = instance_double('Article') allow(article).to receive(:author).and_return(nil)

presenter = described_class.new(article) expect(presenter.title).to include('by an unknown author')

good - verifying object double

article = object_double(Article.new, valid?: true) expect(article.save).to be true

good - verifying partial double

allow(Article).to receive(:find).with(5).and_return(article)

good - verifying class double

notifier = class_double('Notifier') expect(notifier).to receive(:notify).with('suspended as')

NOTE: If you stub a method that could give a false-positive test result, you have gone too far.

=== Dealing with Time

Always use https://github.com/travisjeffery/timecop[Timecop] instead of stubbing anything on Time or Date.

[source,ruby]

describe InvoiceReminder do subject(:time_with_offset) { described_class.new.get_offset_time }

bad

it 'offsets the time 2 days into the future' do current_time = Time.now allow(Time).to receive(:now).and_return(current_time) expect(time_with_offset).to eq(current_time + 2.days) end

good

it 'offsets the time 2 days into the future' do Timecop.freeze(Time.now) do expect(time_with_offset).to eq 2.days.from_now end end end

=== Stub HTTP Requests

Stub HTTP requests when the code is making them. Avoid hitting real external services.

Use https://github.com/bblimke/webmock[webmock] and https://github.com/vcr/vcr[VCR] separately or https://marnen.github.io/webmock-presentation/webmock.html[together].

[source,ruby]

good

context 'with unauthorized access' do let(:uri) { 'http://api.lelylan.com/types' }

before { stub_request(:get, uri).to_return(status: 401, body: fixture('401.json')) }

it 'returns access denied' do page.driver.get uri expect(page).to have_content 'Access denied' end end

[#declare-constants] === Declare Constants

Do not explicitly declare classes, modules, or constants in example groups. https://rspec.info/features/3-12/rspec-mocks/mutating-constants/[Stub constants instead].

NOTE: Constants, including classes and modules, when declared in a block scope, are defined in global namespace, and leak between examples.

[source,ruby]

bad

describe SomeClass do CONSTANT_HERE = 'I leak into global namespace' end

good

describe SomeClass do before do stub_const('CONSTANT_HERE', 'I only exist during this example') end end

bad

describe SomeClass do class FooClass < described_class def double_that some_base_method * 2 end end

it { expect(FooClass.new.double_that).to eq(4) } end

good - anonymous class, no constant needs to be defined

describe SomeClass do let(:foo_class) do Class.new(described_class) do def double_that some_base_method * 2 end end end

it { expect(foo_class.new.double_that).to eq(4) } end

good - constant is stubbed

describe SomeClass do before do foo_class = Class.new(described_class) do def do_something end end stub_const('FooClass', foo_class) end

it { expect(FooClass.new.double_that).to eq(4) } end

[#implicit-block-expectations] === Implicit Block Expectations

Avoid using implicit block expectations.

[source,ruby]

bad

subject { -> { do_something } } it { is_expected.to change(something).to(new_value) }

good

it 'changes something to a new value' do expect { do_something }.to change(something).to(new_value) end

== Naming

=== Context Descriptions

Context descriptions should describe the conditions shared by all the examples within. Full example names (formed by concatenation of all nested block descriptions) should form a readable sentence.

A typical description will be an adjunct phrase starting with 'when', 'with', 'without', or similar words.

[source,ruby]

bad - 'Summary user logged in no display name shows a placeholder'

describe 'Summary' do context 'user logged in' do context 'no display name' do it 'shows a placeholder' do end end end end

good - 'Summary when the user is logged in when the display name is blank shows a placeholder'

describe 'Summary' do context 'when the user is logged in' do context 'when the display name is blank' do it 'shows a placeholder' do end end end end

=== Example Descriptions

it/specify block descriptions should never end with a conditional. This is a code smell that the it most likely needs to be wrapped in a context.

[source,ruby]

bad

it 'returns the display name if it is present' do

...

end

good

context 'when display name is present' do it 'returns the display name' do # ... end end

This encourages the addition of negative test cases that might have

been overlooked

context 'when display name is not present' do it 'returns nil' do # ... end end

=== Keep Example Descriptions Short

Keep example description shorter than 60 characters.

Write the example that documents itself, and generates proper documentation format output.

[source,ruby]

bad

it 'rewrites "should not return something" as "does not return something"' do

...

end

good

it 'rewrites "should not return something"' do expect(rewrite('should not return something')).to eq 'does not return something' end

good - self-documenting

specify do expect(rewrite('should not return something')).to eq 'does not return something' end

=== "Should" in Example Docstrings[[should-in-it]]

Do not write 'should' or 'should not' in the beginning of your example docstrings. The descriptions represent actual functionality, not what might be happening. Use the third person in the present tense.

[source,ruby]

bad

it 'should return the summary' do

...

end

good

it 'returns the summary' do

...

end

=== Describe the Methods[[example-group-naming]]

Be clear about what method you are describing. Use the Ruby documentation convention of . when referring to a class method's name and # when referring to an instance method's name.

[source,ruby]

bad

describe 'the authenticate method for User' do

...

end

describe 'if the user is an admin' do

...

end

good

describe '.authenticate' do

...

end

describe '#admin?' do

...

end

=== Use expect

Always use the newer expect syntax.

Configure RSpec to only accept the new expect syntax.

[source,ruby]

bad

it 'creates a resource' do response.should respond_with_content_type(:json) end

good

it 'creates a resource' do expect(response).to respond_with_content_type(:json) end

== Matchers

=== Predicate Matchers

Use RSpec's predicate matcher methods when possible.

[source,ruby]

describe Article do subject(:article) { FactoryBot.create(:article) }

bad

it 'is published' do expect(article.published?).to be true end

good

it 'is published' do expect(article).to be_published end

even better

it { is_expected.to be_published } end

=== Built in Matchers

Use built-in matchers.

[source,ruby]

bad

it 'includes a title' do expect(article.title.include?('a lengthy title')).to be true end

good

it 'includes a title' do expect(article.title).to include 'a lengthy title' end

=== be Matcher

Avoid using be matcher without arguments. It is too generic, as it pass on everything that is not nil or false. If that is the exact intent, use be_truthy. In all other cases it's better to specify what exactly is the expected value.

[source,ruby]

bad

it 'has author' do expect(article.author).to be end

good

it 'has author' do expect(article.author).to be_truthy # same as the original expect(article.author).not_to be_nil # be is often used to check for non-nil value expect(article.author).to be_an(Author) # explicit check for the type of the value end

=== Extract Common Expectation Parts into Matchers

Extract frequently used common logic from your examples into https://rspec.info/features/3-12/rspec-expectations/custom-matchers/define-matcher/[custom matchers].

[source,ruby]

bad

it 'returns JSON with temperature in Celsius' do json = JSON.parse(response.body).with_indifferent_access expect(json[:celsius]).to eq 30 end

it 'returns JSON with temperature in Fahrenheit' do json = JSON.parse(response.body).with_indifferent_access expect(json[:fahrenheit]).to eq 86 end

good

it 'returns JSON with temperature in Celsius' do expect(response).to include_json(celsius: 30) end

it 'returns JSON with temperature in Fahrenheit' do expect(response).to include_json(fahrenheit: 86) end

=== any_instance_of

Avoid using allow_any_instance_of/expect_any_instance_of. It might be an indication that the object under test is too complex, and is ambiguous when used with receive counts.

[source,ruby]

bad

it 'has a name' do allow_any_instance_of(User).to receive(:name).and_return('Tweedledee') expect(account.name).to eq 'Tweedledee' end

good

let(:account) { Account.new(user) }

it 'has a name' do allow(user).to receive(:name).and_return('Tweedledee') expect(account.name).to eq 'Tweedledee' end

=== Matcher Libraries

Use third-party matcher libraries that provide convenience helpers that will significantly simplify the examples, https://github.com/thoughtbot/shoulda-matchers[Shoulda Matchers] are one worth mentioning.

[source,ruby]

bad

describe '#title' do it 'is required' do article.title = nil article.valid? expect(article.errors[:title]) .to contain_exactly('Article has no title') not end end

good

describe '#title' do it 'is required' do expect(article).to validate_presence_of(:title) .with_message('Article has no title') end end

== Rails: Integration[[integration]][[rails]]

Test what you see. Deeply test your models and your application behaviour (integration tests). Do not add useless complexity testing controllers.

This is an open debate in the Ruby community and both sides have good arguments supporting their idea. People supporting the need of testing controllers will tell you that your integration tests don't cover all use cases and that they are slow. Both are wrong. It is possible to cover all use cases and it's possible to make them fast.

== Rails: Views[[views]]

=== View Directory Structure

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.

=== View Spec File Name

The naming convention for the view specs is adding _spec.rb to the view name, for example the view _form.html.erb has a corresponding spec _form.html.erb_spec.rb.

=== View Outer describe

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.

[source,ruby]

spec/views/articles/new.html.erb_spec.rb

describe 'articles/new.html.erb' do

...

end

=== View Mock Models

Always mock the models in the view specs. The purpose of the view is only to display information.

=== View assign

The method assign supplies the instance variables which the view uses and are supplied by the controller.

[source,ruby]

spec/views/articles/edit.html.erb_spec.rb

describe 'articles/edit.html.erb' do it 'renders the form for a new article creation' do assign(:article, double(Article).as_null_object) render expect(rendered).to have_selector('form', method: 'post', action: articles_path ) do |form| expect(form).to have_selector('input', type: 'submit') end end end

=== Capybara Negative Selectors[[view-capybara-negative-selectors]]

Prefer capybara negative selectors over to_not with positive ones.

[source,ruby]

bad

expect(page).to_not have_selector('input', type: 'submit') expect(page).to_not have_xpath('tr')

good

expect(page).to have_no_selector('input', type: 'submit') expect(page).to have_no_xpath('tr')

=== View Helper Stub

When a view uses helper methods, these methods need to be stubbed. Stubbing the helper methods is done on the template object:

[source,ruby]

app/helpers/articles_helper.rb

class ArticlesHelper def formatted_date(date) # ... end end

[source,ruby]

app/views/articles/show.html.erb

<%= 'Published at: #{formatted_date(@article.published_at)}' %>

[source,ruby]

spec/views/articles/show.html.erb_spec.rb

describe 'articles/show.html.erb' do it 'displays the formatted date of article publishing' do article = double(Article, published_at: Date.new(2012, 01, 01)) assign(:article, article)

allow(template).to_receive(:formatted_date).with(article.published_at).and_return('01.01.2012')

render
expect(rendered).to have_content('Published at: 01.01.2012')

end end

=== View Helpers

The helpers specs are separated from the view specs in the spec/helpers directory.

== Rails: Controllers[[controllers]]

=== Controller Models

Mock the models and stub their methods. Testing the controller should not depend on the model creation.

=== Controller Behaviour

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.

[source,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) { double(Article) }

describe 'POST create' do before { allow(Article).to receive(:new).and_return(article) }

it 'creates a new article with the given attributes' do
  expect(Article).to 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
  expect(article).to receive(:save)
  post :create
end

it 'redirects to the Articles index' do
  allow(article).to receive(:save)
  post :create
  expect(response).to redirect_to(action: 'index')
end

end end

=== Controller Contexts

Use context when the controller action has different behaviour depending on the received params.

[source,ruby]

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) { double(Article) }

describe 'POST create' do before { allow(Article).to receive(:new).and_return(article) }

it 'creates a new article with the given attributes' do
  expect(Article).to 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
  expect(article).to receive(:save)
  post :create
end

context 'when the article saves successfully' do
  before do
    allow(article).to receive(:save).and_return(true)
  end

  it 'sets a flash[:notice] message' do
    post :create
    expect(flash[:notice]).to eq('The article was saved successfully.')
  end

  it 'redirects to the Articles index' do
    post :create
    expect(response).to redirect_to(action: 'index')
  end
end

context 'when the article fails to save' do
  before do
    allow(article).to receive(:save).and_return(false)
  end

  it 'assigns @article' do
    post :create
    expect(assigns[:article]).to eq(article)
  end

  it "re-renders the 'new' template" do
    post :create
    expect(response).to render_template('new')
  end
end

end end

== Rails: Models[[models]]

=== Model Mocks

Do not mock the models in their own specs.

=== Model Objects

Use FactoryBot.create to make real objects, or just use a new (unsaved) instance with subject.

[source,ruby]

describe Article do subject(:article) { FactoryBot.create(:article) }

it { is_expected.to be_an Article } it { is_expected.to be_persisted } end

=== Model Mock Associations

It is acceptable to mock other models or child objects.

=== Avoid Duplication in Model Tests[[model-avoid-duplication]]

Create the model for all examples in the spec to avoid duplication.

[source,ruby]

describe Article do let(:article) { FactoryBot.create(:article) } end

=== Check Model Validity[[model-check-validity]]

Add an example ensuring that the model created with FactoryBot.create is valid.

[source,ruby]

describe Article do it 'is valid with valid attributes' do expect(article).to be_valid end end

=== Model Validations

When testing validations, use expect(model.errors[:attribute].size).to eq(x) to specify the attribute which should be validated. Using be_valid does not guarantee that the problem is in the intended attribute.

[source,ruby]

bad

describe '#title' do it 'is required' do article.title = nil expect(article).to_not be_valid end end

preferred

describe '#title' do it 'is required' do article.title = nil article.valid? expect(article.errors[:title].size).to eq(1) end end

=== Separate Example Group for Attribute Validations[[model-separate-describe-for-attribute-validations]]

Add a separate describe for each attribute which has validations.

[source,ruby]

describe '#title' do it 'is required' do article.title = nil article.valid? expect(article.errors[:title].size).to eq(1) end end

describe '#name' do it 'is required' do article.name = nil article.valid? expect(article.errors[:name].size).to eq(1) end end

=== Naming Another Object[[model-name-another-object]]

When testing uniqueness of a model attribute, name the other object another_object.

[source,ruby]

describe Article do describe '#title' do it 'is unique' do another_article = FactoryBot.create(:article, title: article.title) article.valid? expect(article.errors[:title].size).to eq(1) end end end

== Rails: Mailers[[mailers]]

=== Mailer Mock Model

The model in the mailer spec should be mocked. The mailer should not depend on the model creation.

=== Mailer Expectations

The mailer spec should verify that:

• the subject is correct
• the sender e-mail is correct
• the e-mail is sent to the correct recipient
• the e-mail contains the required information

[source,ruby]

describe SubscriberMailer do let(:subscriber) { double(Subscription, email: '[email protected]', name: 'John Doe') }

describe 'successful registration email' do subject(:email) { SubscriptionMailer.successful_registration_email(subscriber) }

it { is_expected.to have_attributes(subject: 'Successful Registration!', from: ['infor@your_site.com'], to: [subscriber.email]) }

it 'contains the subscriber name' do
  expect(email.body.encoded).to match(subscriber.name)
end

end end

== Recommendations

=== Correct Setup

Correctly set up RSpec configuration globally (~/.rspec), per project (.rspec), and in project override file that is supposed to be kept out of version control (.rspec-local). Use rspec --init to generate .rspec and spec/spec_helper.rb files.

.rspec

--color --require spec_helper

.rspec-local

--profile 2

== Related Guides

• https://rubystyle.guide[Ruby Style Guide]
• https://rails.rubystyle.guide[Rails Style Guide]
• https://minitest.rubystyle.guide[Minitest Style Guide]

== Contributing

Nothing written in this guide is set in stone. Everyone is welcome to contribute, 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!

You can also support the project (and RuboCop) with financial contributions via https://www.patreon.com/bbatsov[Patreon].

=== How to Contribute?

It's easy, just follow the contribution guidelines below:

• https://docs.github.com/en/get-started/quickstart/fork-a-repo[Fork] the https://github.com/rubocop/rspec-style-guide[project] on GitHub
• Make your feature addition or bug fix in a feature branch
• Include a http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html[good description] of your changes
• Push your feature branch to GitHub
• Send a https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests[Pull Request]

== License

image:https://i.creativecommons.org/l/by/3.0/88x31.png[Creative Commons License] This work is licensed under a http://creativecommons.org/licenses/by/3.0/deed.en_US[Creative Commons Attribution 3.0 Unported License]

== Credit

Inspiration was taken from the following:

https://github.com/howaboutwe/rspec-style-guide[HowAboutWe's RSpec style guide]

https://github.com/rubocop/rails-style-guide[Community Rails style guide]

This guide was maintained by https://github.com/reachlocal[ReachLocal] for a long while.

This guide includes material originally present in https://github.com/betterspecs/betterspecs[BetterSpecs] (https://betterspecs.github.io/betterspecs/[newer site] https://www.betterspecs.org/[older site]), sponsored by https://github.com/lelylan[Lelylan] and maintained by https://github.com/andreareginato[Andrea Reginato] and https://github.com/betterspecs/betterspecs/graphs/contributors[many others] for a long while.