el-feo skills

Writing high-quality unit tests for JavaScript and TypeScript using Jest. Covers test structure (AAA pattern, USE naming), breaking dependencies (stubs, mocks, dependency injection), testing async code (promises, callbacks, timers), avoiding flaky tests, and test-driven development. Use when writing tests, debugging test failures, refactoring tests for maintainability, or questions about Jest, TDD, mocks, stubs, or test best practices.

Deploy containerized web applications to any Linux server using Kamal. Use when users need to deploy, configure, debug, or manage Kamal deployments including initial setup, configuration of deploy.yml, deployment workflows, rollbacks, managing accessories (databases, Redis), troubleshooting deployment issues, or understanding Kamal commands and best practices.

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".

Comprehensive ESLint agent for JavaScript/TypeScript code quality. Use when setting up ESLint, configuring linting rules, analyzing code for issues, fixing violations, or integrating ESLint into development workflows. Triggers on requests involving code quality, linting, static analysis, or ESLint configuration for JavaScript, TypeScript, React, or Node.js projects.

Comprehensive Ruby and Rails code review using Sandi Metz rules and SOLID principles. Automatically runs rubycritic and simplecov, analyzes changed files in current branch vs base branch, identifies OOP violations, Rails anti-patterns, security issues, 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, or when user mentions code review, pull request review, or code quality analysis.

Comprehensive Tailscale VPN setup, configuration, and management for mesh networking, secure access, and zero-trust infrastructure. Covers installation, CLI commands, subnet routers, exit nodes, Tailscale SSH, ACL/grants configuration, MagicDNS, Tailscale Serve/Funnel, API automation, and production deployment best practices.

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.

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.

Code review agent based on Sandi Metz's object-oriented design principles from "Practical Object-Oriented Design in Ruby" and "99 Bottles of OOP". Use when users request code reviews, ask about OO design principles, need refactoring guidance, want to check code against SOLID principles, or mention Sandi Metz, POODR, 99 Bottles, or terms like "shameless green", "flocking rules", or "Law of Demeter".

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 BDD testing with Cucumber and Gherkin syntax. Use when writing feature files (.feature), step definitions, hooks, or implementing Behaviour-Driven Development. Covers Gherkin keywords (Feature, Scenario, Given/When/Then, Background, Scenario Outline, Rule), step definition patterns for Ruby/JavaScript/Java/Python, hooks (Before/After/BeforeAll/AfterAll), tags, data tables, doc strings, and best practices. Triggers on cucumber, gherkin, BDD, feature files, step definitions, acceptance testing, executable specifications.

Comprehensive Ruby implementations of Gang of Four (GoF) design patterns. Use when implementing object-oriented design solutions, refactoring to reduce coupling, solving architecture problems, or when user mentions specific patterns (Factory, Singleton, Observer, Strategy, etc.) in Ruby context.

Comprehensive guide for creating software diagrams using Mermaid syntax. Use when users need to create, visualize, or document software through diagrams including class diagrams (domain modeling, object-oriented design), sequence diagrams (application flows, API interactions, code execution), flowcharts (processes, algorithms, user journeys), entity relationship diagrams (database schemas), C4 architecture diagrams (system context, containers, components), state diagrams, git graphs, pie charts, gantt charts, or any other diagram type. Triggers include requests to "diagram", "visualize", "model", "map out", "show the flow", or when explaining system architecture, database design, code structure, or user/application flows.

Ruby static code analyzer and formatter for enforcing style guidelines, detecting bugs, and improving code quality. Supports Rails, RSpec, and Performance extensions with safe autocorrection capabilities.

Create, evaluate, and optimize GitHub Actions workflows and custom actions. Use when building CI/CD pipelines, creating workflow files, developing custom actions, troubleshooting workflow failures, performing security analysis, optimizing performance, or reviewing GitHub Actions best practices. Covers Ruby/Rails, TypeScript/Node.js, Heroku and Fly.io deployments.

Comprehensive Vitest testing framework guide with strong emphasis on Jest-to-Vitest migration. Covers automated migration using codemods, configuration setup, API differences, best practices, and troubleshooting. Use when migrating from Jest, setting up Vitest, writing tests, configuring test environments, or resolving migration issues. Primary focus is seamless Jest migration with minimal code changes.

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.

Comprehensive Ruby development skill covering language fundamentals, object-oriented design patterns, error handling strategies, performance optimization, modern Ruby 3.x features (pattern matching, ractors, typed Ruby), testing patterns, metaprogramming, concurrency, and Rails-specific best practices. Use when writing Ruby code, refactoring, implementing design patterns, handling exceptions, optimizing performance, writing tests, or applying Ruby idioms and conventions.

Create expert-level Ruby on Rails generators for models, services, controllers, and full-stack features. Use when building custom generators, scaffolds, or code generation tools for Rails applications, or when the user mentions Rails generators, Thor DSL, or automated code generation.

Static analysis security vulnerability scanner for Ruby on Rails applications. Use when analyzing Rails code for security issues, running security audits, reviewing code for vulnerabilities, setting up security scanning in CI/CD, managing security warnings, or investigating specific vulnerability types (SQL injection, XSS, command injection, etc.). Also use when configuring Brakeman, reducing false positives, or integrating with automated workflows.