Ruby Tooling

Comprehensive guide to Ruby linting, formatting, type checking, and coverage.

Linting: Standard Ruby (Recommended)

Modern "no config" linting based on RuboCop:

# Gemfile
gem 'standard', group: [:development, :test]

Commands

# Check
bundle exec standardrb

# Autofix
bundle exec standardrb --fix

# Generate TODO for gradual adoption
bundle exec standardrb --generate-todo

Linting: RuboCop (Classic)

# Gemfile
group :development, :test do
  gem 'rubocop', '~> 1.60', require: false
  gem 'rubocop-rails', require: false
  gem 'rubocop-rspec', require: false
  gem 'rubocop-performance', require: false
end

Configuration

# .rubocop.yml
require:
  - rubocop-rails
  - rubocop-rspec
  - rubocop-performance

AllCops:
  NewCops: enable
  TargetRubyVersion: 3.3
  Exclude:
    - 'db/schema.rb'
    - 'bin/*'
    - 'vendor/**/*'

Metrics/MethodLength:
  Max: 20

Metrics/ClassLength:
  Max: 200

Metrics/BlockLength:
  Exclude:
    - 'spec/**/*'
    - '*.gemspec'

Style/Documentation:
  Enabled: false

Commands

# Check
bundle exec rubocop

# Autofix safe cops
bundle exec rubocop -a

# Autofix all (including unsafe)
bundle exec rubocop -A

# Generate TODO
bundle exec rubocop --auto-gen-config

Type Checking: Sorbet

# Gemfile
gem 'sorbet', group: :development
gem 'sorbet-runtime'
gem 'tapioca', group: :development

Setup

bundle exec srb init
bundle exec tapioca init
bundle exec tapioca gems

Commands

# Type check
bundle exec srb tc

Signatures

# typed: strict

class User
  extend T::Sig

  sig { params(name: String, email: String).void }
  def initialize(name:, email:)
    @name = name
    @email = email
  end

  sig { returns(String) }
  attr_reader :name, :email
end

Type Checking: RBS + Steep

# Gemfile
gem 'rbs', group: :development
gem 'steep', group: :development

Commands

bundle exec steep check
bundle exec rbs prototype rb lib/user.rb > sig/user.rbs

Test Coverage: SimpleCov

# Gemfile
gem 'simplecov', require: false, group: :test

Configuration

# spec/spec_helper.rb (at the very top)
require 'simplecov'
SimpleCov.start do
  add_filter '/spec/'
  add_filter '/config/'
  add_group 'Models', 'app/models'
  add_group 'Services', 'app/services'
  minimum_coverage 90
end

Commands

# Run tests with coverage
bundle exec rspec

# Coverage report in coverage/index.html
open coverage/index.html

All-in-One: Rake Tasks

# Rakefile
require 'rspec/core/rake_task'
require 'standard/rake'

RSpec::Core::RakeTask.new(:spec)

desc 'Run all checks'
task check: [:standard, :spec]

desc 'Run checks with autofix'
task fix: ['standard:fix']

task default: :check

Project Validation

Run all checks:

# With Standard Ruby
bundle exec standardrb && bundle exec rspec

# With RuboCop + Sorbet
bundle exec rubocop && bundle exec srb tc && bundle exec rspec

# With coverage
COVERAGE=true bundle exec rspec

CI Configuration

# .github/workflows/ci.yml
name: CI

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4
      - uses: ruby/setup-ruby@v1
        with:
          ruby-version: '3.3'
          bundler-cache: true

      - name: Lint
        run: bundle exec standardrb

      - name: Type check
        run: bundle exec srb tc

      - name: Test
        run: bundle exec rspec

Quick Reference

Operation	Standard Ruby	RuboCop
Lint check	standardrb	rubocop
Lint fix	standardrb --fix	rubocop -A
Type check	srb tc	steep check
Format	(included in lint)	(included in lint)
Coverage	rspec + simplecov	rspec + simplecov
All checks	rake check	rake check

Recommended Stack

• Lint/Format: Standard Ruby (no config debates)
• Types: Sorbet for new projects
• Testing: RSpec with SimpleCov