MSW Skill

Created by Anivar Aravind

An AI agent skill for writing, reviewing, and debugging MSW (Mock Service Worker) v2 handlers, server setup, and test patterns with modern best practices.

The Problem

AI agents often generate outdated MSW v1 patterns — rest.get() instead of http.get(), res(ctx.json(...)) instead of HttpResponse.json(), (req, res, ctx) instead of ({ request, params }) — and miss critical testing best practices like server.boundary() for concurrent tests, onUnhandledRequest: 'error', and proper lifecycle hook setup. These produce code that fails to compile or silently misbehaves at runtime.

This Solution

20 rules with incorrect/correct code examples that teach agents MSW v2's actual API, handler design, server lifecycle, response construction, testing patterns, GraphQL usage, and v1-to-v2 migration. Each rule targets a specific mistake and shows exactly how to fix it.

Install

npx skills add anivar/msw-skill -g

Or with full URL:

npx skills add https://github.com/anivar/msw-skill

Baseline

• msw ^2.0.0
• TypeScript/JavaScript

What's Inside

20 Rules Across 7 Categories

Priority	Category	Rules	Impact
1	Handler Design	4	CRITICAL
2	Setup & Lifecycle	3	CRITICAL
3	Request Reading	2	HIGH
4	Response Construction	3	HIGH
5	Test Patterns	4	HIGH
6	GraphQL	2	MEDIUM
7	Utilities	2	MEDIUM

Each rule file contains:

• Why it matters
• Incorrect code with explanation
• Correct code with explanation
• Decision tables and additional context

6 Deep-Dive References

Reference	Covers
handler-api.md	http.* and graphql.* methods, URL predicates, path params, handler options
response-api.md	HttpResponse class, all 7 static methods, cookie handling
server-api.md	setupServer/setupWorker, lifecycle events, boundary(), onUnhandledRequest
test-patterns.md	Vitest/Jest setup, per-test overrides, concurrent isolation, cache clearing
migration-v1-to-v2.md	Complete v1 to v2 breaking changes with migration mapping
anti-patterns.md	10 common mistakes with BAD/GOOD examples

Structure

├── SKILL.md                          # Entry point for AI agents
├── AGENTS.md                         # Compiled guide with all rules expanded
├── rules/                            # Individual rules (Incorrect/Correct)
│   ├── handler-*                     # Handler design (CRITICAL)
│   ├── setup-*                       # Setup & lifecycle (CRITICAL)
│   ├── request-*                     # Request reading (HIGH)
│   ├── response-*                    # Response construction (HIGH)
│   ├── test-*                        # Test patterns (HIGH)
│   ├── graphql-*                     # GraphQL (MEDIUM)
│   └── util-*                        # Utilities (MEDIUM)
└── references/                       # Deep-dive reference docs
    ├── handler-api.md
    ├── response-api.md
    ├── server-api.md
    ├── test-patterns.md
    ├── migration-v1-to-v2.md
    └── anti-patterns.md

Ecosystem — Skills by Anivar Aravind

Testing Skills

Skill	What it covers	Install
jest-skill	Jest best practices — mock design, async testing, matchers, timers, snapshots	npx skills add anivar/jest-skill -g
zod-testing	Zod schema testing — safeParse, mock data, property-based	npx skills add anivar/zod-testing -g
redux-saga-testing	Redux-Saga testing — expectSaga, testSaga, providers	npx skills add anivar/redux-saga-testing -g

Library & Framework Skills

Skill	What it covers	Install
zod-skill	Zod v4 schema validation, parsing, error handling	npx skills add anivar/zod-skill -g
redux-saga-skill	Redux-Saga effects, fork model, channels, RTK	npx skills add anivar/redux-saga-skill -g

Engineering Analysis

Skill	What it covers	Install
contributor-codebase-analyzer	Code analysis, annual reviews, promotion readiness	npx skills add anivar/contributor-codebase-analyzer -g

Author

Anivar Aravind — Building AI agent skills for modern JavaScript/TypeScript development.

License

MIT