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Bun Jest Migration

Use when migrating from Jest to Bun's test runner, import compatibility, mocks, and config.

By secondsky
20230Updated 1 week agoTypeScriptMIT

Skill Content

# Bun Jest Migration

Bun's test runner is Jest-compatible. Most Jest tests run without changes.

## Quick Migration

```bash
# 1. Remove Jest dependencies
bun remove jest ts-jest @types/jest babel-jest

# 2. Update test script
# package.json: "test": "bun test"

# 3. Run tests
bun test
```

## Import Changes

```typescript
// Before (Jest)
import { describe, it, expect, jest } from '@jest/globals';

// After (Bun) - No import needed, or explicit:
import { describe, test, expect, mock, spyOn } from "bun:test";
```

## API Compatibility

### Fully Compatible

| Jest | Bun | Notes |
|------|-----|-------|
| `describe()` | `describe()` | Identical |
| `it()` / `test()` | `test()` | Use `test()` |
| `expect()` | `expect()` | Same matchers |
| `beforeAll/Each` | `beforeAll/Each` | Identical |
| `afterAll/Each` | `afterAll/Each` | Identical |
| `jest.fn()` | `mock()` | Use `mock()` |
| `jest.spyOn()` | `spyOn()` | Identical |

### Requires Changes

| Jest | Bun Equivalent |
|------|----------------|
| `jest.mock('module')` | `mock.module('module', () => {...})` |
| `jest.useFakeTimers()` | `import { setSystemTime } from "bun:test"` |
| `jest.setTimeout()` | Third argument to `test()` |
| `jest.clearAllMocks()` | Call `.mockClear()` on each mock |

## Mock Migration

### Mock Functions

```typescript
// Jest
const fn = jest.fn().mockReturnValue('value');

// Bun
const fn = mock(() => 'value');
// Or for compatibility:
import { jest } from "bun:test";
const fn = jest.fn(() => 'value');
```

### Module Mocking

```typescript
// Jest (top-level hoisting)
jest.mock('./utils', () => ({
  helper: jest.fn(() => 'mocked')
}));

// Bun (inline, no hoisting)
import { mock } from "bun:test";
mock.module('./utils', () => ({
  helper: mock(() => 'mocked')
}));
```

### Spy Migration

```typescript
// Jest
jest.spyOn(console, 'log').mockImplementation(() => {});

// Bun (identical)
spyOn(console, 'log').mockImplementation(() => {});
```

## Timer Migration

```typescript
// Jest
jest.useFakeTimers();
jest.setSystemTime(new Date('2024-01-01'));
jest.advanceTimersByTime(1000);

// Bun - supports Jest-compatible timer APIs
import { setSystemTime } from "bun:test";
import { jest } from "bun:test";

jest.useFakeTimers();
jest.setSystemTime(new Date('2024-01-01'));
jest.advanceTimersByTime(1000);  // Now supported
```

## Snapshot Testing

```typescript
// Jest
expect(component).toMatchSnapshot();
expect(data).toMatchInlineSnapshot(`"expected"`);

// Bun (identical)
expect(component).toMatchSnapshot();
expect(data).toMatchInlineSnapshot(`"expected"`);
```

Update snapshots:
```bash
bun test --update-snapshots
```

## Configuration Migration

### jest.config.js ā†’ bunfig.toml

```javascript
// jest.config.js (before)
module.exports = {
  testMatch: ['**/*.test.ts'],
  testTimeout: 10000,
  setupFilesAfterEnv: ['./jest.setup.ts'],
  collectCoverage: true,
  coverageThreshold: { global: { lines: 80 } }
};
```

```toml
# bunfig.toml (after)
[test]
root = "./"
preload = ["./jest.setup.ts"]
timeout = 10000
coverage = true
coverageThreshold = 0.8
```

## Common Migration Issues

### Issue: `jest.mock` Not Working

```typescript
// Jest mock hoisting doesn't exist in Bun
// Move mock.module before imports or use dynamic imports

// Solution 1: Use mock.module at top
mock.module('./api', () => ({ fetch: mock() }));
import { fetch } from './api';

// Solution 2: Dynamic import
const mockFetch = mock();
mock.module('./api', () => ({ fetch: mockFetch }));
const { fetch } = await import('./api');
```

### Issue: Timer Functions Missing

```typescript
// Bun timer support is limited
// Use setSystemTime for date mocking
import { setSystemTime } from "bun:test";

beforeEach(() => {
  setSystemTime(new Date('2024-01-01'));
});

afterEach(() => {
  setSystemTime(); // Reset to real time
});
```

### Issue: Custom Matchers

```typescript
// Jest
expect.extend({ toBeWithinRange(received, floor, ceiling) {...} });

// Bun (same API)
import { expect } from "bun:test";
expect.extend({
  toBeWithinRange(received, floor, ceiling) {
    const pass = received >= floor && received <= ceiling;
    return {
      pass,
      message: () => `expected ${received} to be within ${floor}-${ceiling}`
    };
  }
});
```

## Step-by-Step Migration

1. **Remove Jest packages**
   ```bash
   bun remove jest ts-jest @types/jest babel-jest jest-environment-jsdom
   ```

2. **Update package.json**
   ```json
   {
     "scripts": {
       "test": "bun test",
       "test:watch": "bun test --watch",
       "test:coverage": "bun test --coverage"
     }
   }
   ```

3. **Convert jest.config.js to bunfig.toml**

4. **Update imports in test files**
   - Find/replace `@jest/globals` ā†’ `bun:test`
   - Find/replace `jest.fn()` ā†’ `mock()`
   - Find/replace `jest.mock()` ā†’ `mock.module()`

5. **Run and fix**
   ```bash
   bun test 2>&1 | head -50  # Check first errors
   ```

## Common Errors

| Error | Cause | Fix |
|-------|-------|-----|
| `Cannot find module '@jest/globals'` | Old import | Use `bun:test` |
| `jest is not defined` | Global jest | Import from `bun:test` |
| `mock.module is not a function` | Wrong import | `import { mock } from "bun:test"` |
| `Snapshot mismatch` | Different serialization | Update with `--update-snapshots` |

## When to Load References

Load `references/compatibility-matrix.md` when:
- Full Jest API compatibility details
- Unsupported features list
- Workarounds for missing features

How to use

  1. Copy the skill content above
  2. Create a .claude/skills directory in your project
  3. Save as .claude/skills/claude-skills-bun-jest-migration.md
  4. Use /claude-skills-bun-jest-migration in Claude Code to invoke this skill

README

View on GitHub

Claude Code Skills Collection

142 production-ready skills for Claude Code CLI

Version 3.5.0 | Last Updated: 2026-07-18

<div align="center">

šŸ”Œ Platform Support

This repository uses Claude Plugin Patterns ā€” natively supported by:

PlatformStatusNotes
Claude Codeāœ… NativeFull marketplace support
Factory Droidāœ… NativeFull marketplace support
</div> **For all other Platforms like opencode, codex and others, you can use https://github.com/enulus/OpenPackage **

A curated collection of battle-tested skills for building modern web applications with Cloudflare, AI integrations, React, Tailwind, and more.

PS: if skills.sh warns about any skill: Their scan process is a outdated LLM which flags newest versions pins (like in ZOD) as non existent and by that potentially malicous.

Quick Start

Marketplace Installation (Recommended)

# Add the marketplace
/plugin marketplace add https://github.com/secondsky/claude-skills

# Install individual skills as needed
/plugin install cloudflare-d1@claude-skills
/plugin install tailwind-v4-shadcn@claude-skills
/plugin install gemini-cli@claude-skills

See MARKETPLACE.md for complete catalog of all 139 skills.

Bulk Installation (Contributors)

# Clone the repository
git clone https://github.com/secondsky/claude-skills.git
cd claude-skills

# Install all 139 skills at once
./scripts/install-all.sh

# Or install individual skills
./scripts/install-skill.sh cloudflare-d1

Repository Structure

This repository contains 139 production-tested skills for Claude Code, each focused on a specific technology or capability.

Individual Skills: Each skill is a standalone unit with:

  • SKILL.md - Core knowledge and guidance
  • Templates - Working code examples
  • References - Extended documentation
  • Scripts - Helper utilities

Installation Options:

  1. Individual - Install only the skills you need via marketplace
  2. Bulk - Install all 139 skills using ./scripts/install-all.sh

Available Skills (139 Individual Skills)

Each skill is individually installable. Install only the skills you need.

Full Catalog: See MARKETPLACE.md for detailed listings.

Categories

CategorySkillsExamples
tooling22turborepo, plan-interview, code-review
frontend26nuxt-v4, nuxt-v5, tailwind-v4-shadcn, tanstack-query, nuxt-studio, maz-ui, threejs
cloudflare21cloudflare-d1, cloudflare-workers-ai, cloudflare-agents
api16api-design-principles, graphql-implementation
ai7gemini-cli, ml-model-training, tanstack-ai
web10hono-routing, firecrawl-scraper, web-performance
security5csrf-protection, xss-prevention
mobile5react-native-app, react-native-skills
woocommerce4woocommerce-backend-dev
testing4vitest-testing, playwright-testing
design4design-review, design-system-creation
auth4better-auth
architecture3microservices-patterns, architecture-patterns
data2recommendation-engine, recommendation-system
cms2hugo, wordpress-plugin-core
database1drizzle-orm-d1
seo2seo-optimizer, seo-keyword-cluster-builder
documentation1technical-specification

How It Works

Auto-Discovery

Claude Code automatically checks ~/.claude/skills/ for relevant skills before planning tasks:

User: "Set up a Cloudflare Worker with D1 database"
           ā†“
Claude: [Checks skills automatically]
           ā†“
Claude: "Found cloudflare-d1 skills.
         These prevent 12 documented errors. Use them?"
           ā†“
User: "Yes"
           ā†“
Result: Production-ready setup, zero errors, ~65% token savings

Note: Due to token limits, not all skills may be visible at once. See āš ļø Important: Token Limits below.

Skill Structure

Each skill includes:

skills/[skill-name]/
ā”œā”€ā”€ SKILL.md              # Complete documentation
ā”œā”€ā”€ .claude-plugin/
ā”‚   ā””ā”€ā”€ plugin.json       # Plugin metadata
ā”œā”€ā”€ templates/            # Ready-to-copy templates
ā”œā”€ā”€ scripts/              # Automation scripts
ā””ā”€ā”€ references/           # Extended documentation

Recent Additions

July 2026

Offensive Security (new category):

  • cybersecurity ā€” Unified OSS-only cybersecurity skill with progressive disclosure. Fuses 7 community skills (mukul975 business-logic/XSS/host-header/forced-browsing/open-redirect, rysweet/amplihack cybersecurity-analyst, Aradotso security-detections-mcp) ported to fully open-source tooling (OWASP ZAP, Dalfox, ffuf, Nuclei, mitmproxy, interact.sh, Semgrep, Sigma). Covers threat modeling (STRIDE/PASTA/VAST, MITRE ATT&CK), web-vuln testing, SAST, code audit, AI/LLM-app security, and detection engineering. Live-target testing is gated behind an authorization disclaimer; static analysis, code review, and threat modeling are always available. Cross-references the 5 existing defensive security plugins (csrf-protection, xss-prevention, vulnerability-scanning, security-headers-configuration, defense-in-depth-validation) for remediation. Integrates 20 Aradotso dev-security skills across 5 grouped reference docs.

May 2026

Supply Chain Security (cross-cutting):

  • dependency-upgrade expanded with Socket CLI integration ā€” proactive malicious package detection, typosquatting alerts, and CI/CD security gates. New 418-line reference guide, 2 GitHub Actions templates, and expanded supply chain security comparison (3 tools)
  • 31 skills now include "Secure Installation" guidance ā€” contextually-tailored security sections across all high-risk skill categories (scaffolding, MCP/agent SDKs, multi-provider installs, Docker, CI/CD). Covers 8 Bun skills, 5 Nuxt skills, 6 Cloudflare skills, 4 AI/agent skills, and 8 frontend/tooling skills
  • Supply chain security is now a first-class cross-cutting concern woven into the skill collection ā€” not a standalone topic

February - April 2026

Full-Stack Frameworks:

  • nuxt-v5 (v1.0.0) - Full Nuxt 5 support with 4 skills (core, data, server, production), 3 diagnostic agents, and interactive setup wizard
  • threejs (v1.0.0) - 3D web graphics: scenes, geometries, shaders, animations, post-processing

Infrastructure:

  • JSON schema validation - Automated plugin.json validation with CI support
  • GitHub issue templates - Skill-specific issue templates for bug reports, feature requests, and submissions

Plugin Enhancements:

  • mutation-testing - Added Bun native runner support
  • dependency-upgrade - Added supply chain security content

December 2025 - January 2026

Frontend Expansion:

  • nuxt-studio (v1.0.0) - Visual CMS for Nuxt Content with live preview, OAuth auth, and R2 storage integration
  • maz-ui (v1.0.0) - 50+ Vue/Nuxt components with theming, i18n, form generation, and 14 composables

Developer Workflow:

  • plan-interview (v2.0.0) - Adaptive interview-driven spec generation with autonomous quality review
  • turborepo (v2.8.0) - Updated to official Vercel skill with enhanced monorepo build optimization

Mobile Development:

  • react-native-skills (v1.0.0) - React Native & Expo best practices with performance optimization patterns

Enhanced Authentication:

  • better-auth (v2.2.0) - Expanded to 18 framework integrations with 30+ authentication plugins

āš ļø Important: Token Limits

Skill Visibility Constraint

Claude Code has a 15,000 character limit for the total size of skill descriptions in the system prompt. This limit also applies to commands and agents.

What this means:

  • Not all 139 skills may be visible in Claude's context at once
  • Skills are loaded based on relevance and available token budget
  • You can verify how many skills Claude currently sees by asking: "How many skills do you see in your system prompt?"

Checking Visible Skills

To verify which skills are currently loaded:

# Ask Claude Code directly
"Check what skills/plugins you see in your system prompt"

Claude will report something like: "85 of 139 skills visible due to token limits"

Workaround: Increase Token Budget

You can double the headroom for skill descriptions by setting an environment variable:

# Increase limit to 30,000 characters
export SLASH_COMMAND_TOOL_CHAR_BUDGET=30000

# Then launch Claude Code
claude

This gives you approximately 2x more skill visibility in the system prompt.

Note: This is a temporary workaround. The Claude Code team is working on better solutions for skill discovery and loading.

Token Efficiency

MetricManual SetupWith SkillsSavings
Average Tokens12,000-15,0004,000-5,000~65%
Typical Errors2-4 per service0 (prevented)100%
Setup Time2-4 hours15-45 minutes~80%

Across all 139 skills: 400+ documented errors prevented.

Contributing

Prerequisites for Contributors

Install the official plugin development toolkit:

/plugin install plugin-dev@claude-code-marketplace

This provides:

  • /plugin-dev:create-plugin command (8-phase guided workflow)
  • 7 comprehensive skills (hooks, MCP, structure, agents, commands, skills)
  • 2 specialized agents (agent-creator, plugin-validator)

Quick Steps

  1. Create skill directory in plugins/
  2. Add SKILL.md with YAML frontmatter
  3. Run ./scripts/sync-plugins.sh
  4. Submit pull request

See CONTRIBUTING.md and PLUGIN_DEV_BEST_PRACTICES.md for detailed guidelines.

Documentation

DocumentPurpose
START_HERE.mdStart here! Quick navigation guide
PLUGIN_DEV_BEST_PRACTICES.mdRepository-specific best practices (marketplace, budget, quality)
MARKETPLACE.mdFull skill catalog and installation guide
MARKETPLACE_MANAGEMENT.mdTechnical infrastructure (plugin.json, scripts, validation)
CLAUDE.mdProject context and development standards
CONTRIBUTING.mdContribution guidelines

Links

Built with ā¤ļø by Claude Skills Maintainers

View source on GitHub