Ruby Rails

Ruby language conventions, idioms, and modern features (3.x+) for writing idiomatic Ruby code. Covers error handling patterns, performance optimization, and Ruby-specific idioms. Use when writing or reviewing pure Ruby code, using modern Ruby features (pattern matching, ractors, RBS), optimizing Ruby performance, or establishing Ruby conventions. For Rails-specific guidance use the rails skill. For design patterns use design-patterns-ruby. For testing use rspec. For code style use rubocop.

Comprehensive Ruby on Rails v8.1 development guide with detailed documentation for Active Record, controllers, views, routing, testing, jobs, mailers, and more. Use when working on Rails applications, building Rails features, debugging Rails code, writing migrations, setting up associations, configuring Rails apps, or answering questions about Rails best practices and patterns.

Comprehensive RSpec testing for Ruby and Rails applications. Covers model specs, request specs, system specs, factories, mocks, and TDD workflow. Automatically triggers on RSpec-related keywords and testing scenarios.

Diagnose and fix slow RSpec test suites using TestProf and proven optimization techniques. Use this skill whenever the user mentions slow tests, test suite performance, RSpec speed, profiling specs, TestProf, TagProf, let_it_be, TPS profiler, or complains that their test suite takes too long. Also use it when the user sees high GC time in tests, wants to parallelize with test-queue, or asks which profiler to run against an RSpec suite. Prefer this skill over generic performance advice whenever RSpec is in the picture.

Comprehensive test coverage analysis and improvement for Ruby and Rails applications using SimpleCov and SimpleCov Console formatter. Automatically runs coverage reports, identifies gaps, suggests tests, and enforces coverage standards. Integrates with RubyCritic for holistic code quality. Use when running tests, analyzing coverage, improving test suites, or setting up coverage tracking in Ruby/Rails projects.

Integrate RubyCritic to analyze Ruby code quality and maintain high standards throughout development. Use when working on Ruby projects to check code smells, complexity, and duplication. Triggers include creating/editing Ruby files, refactoring code, reviewing code quality, or when user requests code analysis or quality checks.

BDD testing with Cucumber and Gherkin for Ruby and Rails applications. Use when writing feature files (.feature), step definitions, hooks, or implementing Behaviour-Driven Development in Ruby/Rails projects. Covers Gherkin keywords (Feature, Scenario, Given/When/Then, Background, Scenario Outline, Rule), Ruby step definition patterns, Cucumber Expressions, hooks (Before/After/BeforeAll/AfterAll), tags, data tables, doc strings, World modules, and Capybara integration. Triggers on cucumber, gherkin, BDD, feature files, step definitions, acceptance testing, executable specifications.

Create expert-level Ruby on Rails generators for models, services, controllers, and full-stack features, plus application templates for whole-app setup. Use when building custom generators, scaffolds, code generation tools, or Rails application templates (rails new -m, app:template, starter-app automation, multi-tenant setup), or when the user mentions Rails generators, Thor DSL, or automated code generation.

Comprehensive Ruby and Rails code review using Sandi Metz rules and SOLID principles. Analyzes changed files in current branch vs base branch, runs rubycritic and simplecov, identifies OOP violations, Rails anti-patterns, security issues, code smells, and test coverage gaps. Outputs REVIEW.md with VSCode-compatible file links. Use when reviewing Ruby/Rails code, conducting code reviews, checking for design issues, pull request review, code quality analysis, or when user mentions Sandi Metz, POODR, 99 Bottles, SOLID, Law of Demeter, or "Tell Don't Ask".

Comprehensive PostgreSQL configuration and usage analysis for Rails applications. Use when Claude Code needs to analyze a Rails codebase for database performance issues, optimization opportunities, or best practice violations. Detects N+1 queries, missing indexes, suboptimal database configurations, anti-patterns, and provides actionable recommendations. Ideal for performance audits, optimization tasks, or when users ask to "analyze the database", "check for N+1 queries", "optimize PostgreSQL", "review database performance", or "suggest database improvements".