Validate test effectiveness with mutation testing using Stryker (TypeScript/JavaScript) and mutmut (Python). Find weak tests that pass despite code mutations. Use when user mentions mutation testing, Stryker, mutmut, test effectiveness, finding weak tests, or improving test quality through mutation analysis.
How to write idiomatic assertions with the Bupkis assertion library for TypeScript and JavaScript
This skill should be used when writing test cases, fixing bugs, analyzing code for potential issues, or improving test coverage for JavaScript/TypeScript applications. Use this for unit tests, integration tests, end-to-end tests, debugging runtime errors, logic bugs, performance issues, security vulnerabilities, and systematic code analysis.
HTTP API testing for TypeScript (Supertest) and Python (httpx, pytest). Covers REST APIs, GraphQL, request/response validation, authentication, and error handling. Use when user mentions API testing, Supertest, httpx, REST testing, endpoint testing, HTTP response validation, or testing API routes.
Implement comprehensive testing strategies using Jest, Vitest, and Testing Library for unit tests, integration tests, and end-to-end testing with mocking, fixtures, and test-driven development. Use when writing JavaScript/TypeScript tests, setting up test infrastructure, or implementing TDD/BDD workflows.
Vitest test runner for JavaScript and TypeScript. Fast, modern alternative to Jest. Vite-native, ESM support, watch mode, UI mode, coverage, mocking, snapshot testing. Use when setting up tests for Vite projects, migrating from Jest, or needing fast test execution.
Fast JavaScript package management with Bun - install, add, remove, update dependencies with optimized CLI flags for agentic workflows.
Decision guide for code navigation. Teaches when to use gabb tools vs default tools (Grep/Read) for maximum efficiency. Applies to Python/TypeScript/Rust/Kotlin/C++.
Update Bun lockfiles (bun.lockb) with proper dependency management. Covers bun update, bun install, lockfile regeneration, and security audits. Use when user mentions bun lockfile, bun update, bun.lockb, updating Bun dependencies, or resolving Bun lockfile conflicts.
Knip finds unused files, dependencies, exports, and types in JavaScript/TypeScript projects. Plugin system for frameworks (React, Next.js, Vite), test runners (Vitest, Jest), and build tools. Use when cleaning up codebases, optimizing bundle size, or enforcing strict dependency hygiene in CI.
Write TypeScript and JavaScript code like a top engineer using functional programming principles. Use when writing new code, reviewing existing code, or refactoring TS/JS projects. Applies pure functions, immutability, function composition, higher-order functions, declarative style, and avoiding shared state using native patterns only (no external libraries). Always analyzes the existing codebase first to understand patterns and conventions before making changes or suggestions.
TypeScript and JavaScript expert with deep knowledge of type-level programming, performance optimization, monorepo management, migration strategies, and modern tooling. Use PROACTIVELY for any TypeScript/JavaScript issues including complex type gymnastics, build performance, debugging, and architectural decisions. If a specialized expert is a better fit, I will recommend switching and stop.
Interactive debugger for Deno/TypeScript applications using the V8 Inspector Protocol. This skill should be used when investigating issues in Deno applications, including memory leaks, performance bottlenecks, race conditions, crashes, or any runtime behavior that requires step-by-step debugging, heap analysis, or CPU profiling. Provides CDP client tools, heap/CPU analyzers, and investigation tracking.
Detects timing side-channel vulnerabilities in cryptographic code. Use when implementing or reviewing crypto code, encountering division on secrets, secret-dependent branches, or constant-time programming questions in C, C++, Go, Rust, Swift, Java, Kotlin, C#, PHP, JavaScript, TypeScript, Python, or Ruby.
TypeScript Language Server Protocol capabilities for navigating TypeScript/JavaScript code. Resolves imported symbols to their definitions (including node_modules), finds all references to functions/classes/variables, gets type information and signatures, previews rename impacts, and checks TypeScript diagnostics. Use when you need to find where ToolLoopAgent or other imports are defined, locate all usages of a function, see TypeScript types, or get compiler errors.
Interact with MCP (Model Context Protocol) servers using the mcporter CLI. Use this skill when you need to list available MCP servers, view tool schemas, call MCP tools, manage OAuth authentication, or generate CLI wrappers and TypeScript types for MCP servers.
Stripe payments integration guide for TypeScript SaaS. Load whenever implementing payments, subscriptions, billing, webhooks, or the customer portal. Covers SDK setup, products/prices, checkout sessions, webhook handling with idempotency, subscription lifecycle, and the customer portal. Load whenever you see Stripe imports or the user mentions payments, billing, subscriptions, or Stripe.
Integrates Nevermined payment infrastructure into AI agents, MCP servers, Google A2A agents, and REST APIs. Handles x402 protocol, credit billing, payment plans, and SDK integration for TypeScript (@nevermined-io/payments) and Python (payments-py).
TypeScript library and CLI for Monarch Money budget management. Search transactions by date/merchant/amount, update categories, list accounts and budgets, manage authentication. Use when user asks about Monarch Money transactions, wants to categorize spending, needs to find specific transactions, or wants to automate budget tasks.
Strict typing and modern TS patterns.
