mern-ninja

MERN Ninja

MERN stack mastery tools for Claude Code

A plugin that supercharges Claude Code with specialized skills for MongoDB, Express, React, and Node.js development.

Installation

# Step 1: Add the marketplace (one-time)
/plugin marketplace add 9tykeshav/mern-ninja-marketplace

# Step 2: Install the plugin
/plugin install mern-ninja@mern-ninja-marketplace

Skills

mern-ninja:backend-test-writer

Generates comprehensive backend tests with smart defaults and zero config.

Just ask:

Generate tests for my user routes
Write tests for the auth service
Create tests for my User model

What it does:

File Type	Test Type	Approach
Routes/Controllers	Integration	Supertest + mongodb-memory-server
Services	Unit	Mocked dependencies
Models	Unit	Validation, methods, toJSON
Middleware	Unit	Mock req/res/next
Utilities	Unit	Pure function tests

Features:

• Auto-detects test framework (Jest/Vitest/Mocha)
• Gap analysis on existing tests before generating new ones
• Priority levels (P0/P1/P2) for each test case
• Domain-specific edge cases (dates → DST/timezone, money → precision)
• Setup/teardown boilerplate included

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mern-ninja:code-reviewer

Reviews MERN stack code for security, performance, and best practices.

Just ask:

Review my authentication code
Check this Express API for security issues
Audit this MongoDB schema

Review priorities:

Priority	Focus
1. Security	Injection, XSS, auth flaws, secrets, CORS
2. Performance	N+1 queries, re-renders, blocking ops
3. Best Practices	Error handling, async patterns, cleanup
4. Architecture	API design, state sync, type safety

Sample output:

# MERN Code Review

## Summary
- Files reviewed: 5
- Issues: 2 Critical, 3 Important, 5 Suggestions

## Critical (Must Fix)
### [C1] Security: NoSQL injection in login
**File:** `api/auth/login.js:24`
**Why:** User input passed directly to query
**Fix:** Use explicit field matching

## What's Good
- Proper JWT refresh flow
- Consistent error responses

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mern-ninja:mongodb-query-patterns

Data-flow-first approach to writing MongoDB/Mongoose queries that scale.

Triggers automatically when you:

Write a new Mongoose query
Wire data between services
Build an endpoint that reads/writes to MongoDB
Pass an ID where a document could be passed instead

Core principle: The best query is the one you never make. Pass documents through the call stack — don't re-fetch what the caller already has.

Patterns covered:

Pattern	What It Prevents
Pass data through services	Same document fetched 3-4x across service boundaries
Batch with $in + Map	N+1 loops that fire one query per item
.select() + .lean()	Full-document fetches with Mongoose overhead on read paths
Avoid .populate() on lists	Hidden N+1 queries behind a clean API
Direct updateOne	Fetch-modify-save round-trips for simple field updates
bulkWrite	Sequential update loops
Hoist common queries	Duplicate queries across if/else branches
Index filter fields	Full collection scans (COLLSCAN)

Includes: Pre-commit checklist, common mistakes table, and the "every query must justify its existence" decision framework.

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Reference Guides

The plugin includes ~1,500 lines of curated best practices:

Guide	Coverage
security.md	OWASP Top 10, MERN-specific vulnerabilities
react.md	Hooks, re-renders, security, testing
nodejs.md	Async patterns, event loop, memory
express.md	Middleware, auth, error handling
mongodb.md	Schema design, indexing, queries
fullstack.md	API design, auth flows, state sync
test-patterns.md	Complete test examples by file type
test-setup.md	Jest config, fixtures, mocking

Roadmap

• mern-ninja:scaffolder – Generate MERN boilerplate
• mern-ninja:migrator – Database migration helper
• mern-ninja:frontend-test-writer – React component tests

License

MIT