Rspec

RSpec Testing Skill

Expert guidance for writing comprehensive tests in RSpec for Ruby and Rails applications. This skill provides immediate, actionable testing strategies with deep-dive references for complex scenarios.

Quick Start

Basic RSpec Structure

# spec/models/user_spec.rb
RSpec.describe User, type: :model do
  describe '#full_name' do
    it 'returns the first and last name' do
      user = User.new(first_name: 'John', last_name: 'Doe')
      expect(user.full_name).to eq('John Doe')
    end
  end
end

Key concepts:

• describe: Groups related tests (classes, methods)
• context: Describes specific scenarios
• it: Individual test example
• expect: Makes assertions using matchers

Running Tests

# Run all specs
bundle exec rspec

# Run specific file
bundle exec rspec spec/models/user_spec.rb

# Run specific line
bundle exec rspec spec/models/user_spec.rb:12

# Run with documentation format
bundle exec rspec --format documentation

# Run only failures from last run
bundle exec rspec --only-failures

Core Testing Patterns

1. Model Specs

Test business logic, validations, associations, and methods:

RSpec.describe Article, type: :model do
  # Test validations
  describe 'validations' do
    it { should validate_presence_of(:title) }
    it { should validate_length_of(:title).is_at_most(100) }
  end

  # Test associations
  describe 'associations' do
    it { should belong_to(:author) }
    it { should have_many(:comments) }
  end

  # Test instance methods
  describe '#published?' do
    context 'when publish_date is in the past' do
      it 'returns true' do
        article = Article.new(publish_date: 1.day.ago)
        expect(article.published?).to be true
      end
    end

    context 'when publish_date is in the future' do
      it 'returns false' do
        article = Article.new(publish_date: 1.day.from_now)
        expect(article.published?).to be false
      end
    end
  end

  # Test scopes
  describe '.recent' do
    it 'returns articles from the last 30 days' do
      old = create(:article, created_at: 31.days.ago)
      recent = create(:article, created_at: 1.day.ago)

      expect(Article.recent).to include(recent)
      expect(Article.recent).not_to include(old)
    end
  end
end

2. Request Specs

Test HTTP requests and responses across the entire stack:

RSpec.describe 'Articles API', type: :request do
  describe 'GET /articles' do
    it 'returns all articles' do
      create_list(:article, 3)

      get '/articles'

      expect(response).to have_http_status(:success)
      expect(JSON.parse(response.body).size).to eq(3)
    end
  end

  describe 'POST /articles' do
    context 'with valid params' do
      it 'creates a new article' do
        article_params = { article: { title: 'New Article', body: 'Content' } }

        expect {
          post '/articles', params: article_params
        }.to change(Article, :count).by(1)

        expect(response).to have_http_status(:created)
      end
    end

    context 'with invalid params' do
      it 'returns errors' do
        invalid_params = { article: { title: '' } }

        post '/articles', params: invalid_params

        expect(response).to have_http_status(:unprocessable_entity)
      end
    end
  end

  describe 'authentication' do
    it 'requires authentication for create' do
      post '/articles', params: { article: { title: 'Test' } }

      expect(response).to have_http_status(:unauthorized)
    end

    it 'allows authenticated users to create' do
      user = create(:user)

      post '/articles',
        params: { article: { title: 'Test' } },
        headers: { 'Authorization' => "Bearer #{user.token}" }

      expect(response).to have_http_status(:created)
    end
  end
end

3. System Specs (End-to-End)

Test user workflows through the browser with Capybara:

RSpec.describe 'Article management', type: :system do
  before { driven_by(:selenium_chrome_headless) }

  scenario 'user creates an article' do
    visit new_article_path

    fill_in 'Title', with: 'My Article'
    fill_in 'Body', with: 'Article content'
    click_button 'Create Article'

    expect(page).to have_content('Article was successfully created')
    expect(page).to have_content('My Article')
  end

  scenario 'user edits an article' do
    article = create(:article, title: 'Original Title')

    visit article_path(article)
    click_link 'Edit'

    fill_in 'Title', with: 'Updated Title'
    click_button 'Update Article'

    expect(page).to have_content('Updated Title')
    expect(page).not_to have_content('Original Title')
  end

  # Test JavaScript interactions
  scenario 'user filters articles', js: true do
    create(:article, title: 'Ruby Article', category: 'ruby')
    create(:article, title: 'Python Article', category: 'python')

    visit articles_path

    select 'Ruby', from: 'filter'

    expect(page).to have_content('Ruby Article')
    expect(page).not_to have_content('Python Article')
  end
end

Factory Bot Integration

Use FactoryBot for test data. Define factories in spec/factories/, use traits for variations, and prefer build over create when persistence isn't needed.

See references/factory_bot.md for factory definitions, traits, sequences, associations, and build strategies.

Essential Matchers

See references/matchers.md for the complete matcher reference.

Mocks, Stubs, and Doubles

Use double or instance_double (preferred — verifies against real class) for test doubles. Stub with allow(obj).to receive(:method), set expectations with expect(obj).to receive(:method), and verify after the fact with spies via have_received.

See references/mocking.md for test doubles, stubbing, message expectations, and spies.

DRY Testing Techniques

Use let (lazy) and let! (eager) for test data, before hooks for shared setup, shared_examples for reusable test groups, and shared_context for reusable setup blocks. Prefer subject for the object under test.

See references/core_concepts.md for detailed coverage of hooks, let, shared examples, shared contexts, and subject.

TDD Workflow

Red-Green-Refactor Cycle

1. Red: Write a failing test first

describe User do
  it 'has a full name' do
    user = User.new(first_name: 'John', last_name: 'Doe')
    expect(user.full_name).to eq('John Doe')
  end
end
# Fails: undefined method `full_name'

2. Green: Write minimal code to pass

class User
  def full_name
    "#{first_name} #{last_name}"
  end
end
# Passes!

3. Refactor: Improve code while keeping tests green

Testing Strategy

Start with system specs for user-facing features:

• Tests complete workflows
• Highest confidence
• Slowest to run

Drop to request specs for API/controller logic:

• Test HTTP interactions
• Faster than system specs
• Cover authentication, authorization, edge cases

Use model specs for business logic:

• Test calculations, validations, scopes
• Fast and focused
• Most of your test suite

Configuration Best Practices

spec/rails_helper.rb

require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'
require_relative '../config/environment'
abort("Run in production!") if Rails.env.production?
require 'rspec/rails'

# Auto-require support files
Dir[Rails.root.join('spec', 'support', '**', '*.rb')].sort.each { |f| require f }

RSpec.configure do |config|
  # Use transactional fixtures
  config.use_transactional_fixtures = true

  # Infer spec type from file location
  config.infer_spec_type_from_file_location!

  # Filter Rails backtrace
  config.filter_rails_from_backtrace!

  # Include FactoryBot methods
  config.include FactoryBot::Syntax::Methods

  # Include request helpers
  config.include RequestHelpers, type: :request

  # Capybara configuration for system specs
  config.before(:each, type: :system) do
    driven_by :selenium_chrome_headless
  end
end

spec/spec_helper.rb

RSpec.configure do |config|
  # Show detailed failure messages
  config.example_status_persistence_file_path = "spec/examples.txt"

  # Disable monkey patching (use expect syntax only)
  config.disable_monkey_patching!

  # Output warnings
  config.warnings = true

  # Profile slowest tests
  config.profile_examples = 10 if ENV['PROFILE']

  # Run specs in random order
  config.order = :random
  Kernel.srand config.seed
end

Common Patterns

For testing background jobs, mailers, file uploads, pagination, and search, see references/rails_testing.md.

Performance Tips

1. Use let instead of before for lazy loading

2. Avoid database calls when testing logic (use mocks)

3. Use build instead of create when persistence isn't needed

4. Use build_stubbed for non-persisted objects with associations

5. Tag slow tests and exclude them during development:

   it 'slow test', :slow do
     # test code
   end
   
   # Run with: rspec --tag ~slow
   

When to Use Each Spec Type

• Model specs: Business logic, calculations, validations, scopes
• Request specs: API endpoints, authentication, authorization, JSON responses
• System specs: User workflows, JavaScript interactions, form submissions
• Mailer specs: Email content, recipients, attachments
• Job specs: Background job enqueueing and execution
• Helper specs: View helper methods
• Routing specs: Custom routes (usually not needed)

Quick Reference

Most Common Commands:

rspec                          # Run all specs
rspec spec/models              # Run model specs
rspec --tag ~slow              # Exclude slow specs
rspec --only-failures          # Rerun failures
rspec --format documentation   # Readable output
rspec --profile               # Show slowest specs

Most Common Matchers:

• eq(expected) - value equality
• be_truthy / be_falsy - truthiness
• include(item) - collection membership
• raise_error(Error) - exceptions
• change { }.by(n) - state changes

Most Common Stubs:

• allow(obj).to receive(:method) - stub method
• expect(obj).to receive(:method) - expect call
• double('name', method: value) - create double

Reference Documentation

For detailed information on specific topics, see the references directory:

• Core Concepts - Describe blocks, contexts, hooks, subject, let
• Matchers Guide - Complete matcher reference with examples
• Mocking and Stubbing - Test doubles, stubs, spies, message expectations
• Rails Testing - Rails-specific spec types and helpers
• Factory Bot - Test data strategies and patterns
• Best Practices - Testing philosophy, patterns, and anti-patterns
• Configuration - Setup, formatters, and optimization

Common Scenarios

For debugging failing tests, testing complex queries, and testing callbacks, see references/rails_testing.md.

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