skills.rest
hubeiqiao
hubeiqiaoCOMMUNITY
Explore all skills by this author →
Website𝕏@hubeiqiaoGitHub

nextjs-middleware-vitest-jsdom

Mock NextResponse methods to test Next.js middleware in jsdom with Vitest.

Updated Mar 4, 2026
Search Tags:#vitest#testing#middleware#next.js#headers#jsdom#response
One-click install
npx skills add https://github.com/hubeiqiao/skills --skill nextjs-middleware-vitest-jsdom
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: nextjs-middleware-vitest-jsdom
Source: https://github.com/hubeiqiao/skills/tree/main/nextjs-middleware-vitest-jsdom
Command: npx skills add https://github.com/hubeiqiao/skills --skill nextjs-middleware-vitest-jsdom

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill resolves the "request.headers must be an instance of Headers" error encountered when testing Next.js middleware with Vitest in a jsdom environment, enabling seamless middleware integration testing.

Core Features & Use Cases

  • Mocking NextResponse: Bypasses the jsdom/edge-runtime Headers class mismatch by mocking NextResponse.next() and NextResponse.redirect().
  • Preserves Testability: Allows testing of status, headers, and cookies without altering the core NextRequest object.
  • Use Case: Debugging and ensuring the correct functioning of locale detection, redirect logic, or cookie handling within your Next.js middleware without relying on the edge runtime.

Quick Start

Apply the provided TypeScript mock to your Vitest setup before importing your middleware.

Frequently Asked Questions about nextjs-middleware-vitest-jsdom

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I fix the "request.headers must be an instance of Headers" error when testing Next.js middleware with Vitest?▼

To fix the "request.headers must be an instance of Headers" error in Next.js middleware testing, you can mock NextResponse.next() and NextResponse.redirect() to bypass jsdom and edge-runtime Headers class mismatches while preserving testable response properties.

How do I test Next.js middleware redirects and locale detection in a jsdom environment?▼

Testing Next.js middleware redirects and locale detection in jsdom involves mocking NextResponse methods to bypass edge runtime mismatches, allowing you to validate redirect logic and cookie handling without altering the core NextRequest object.

Can I test Next.js middleware outside the edge runtime using Vitest?▼

Yes, you can test Next.js middleware outside the edge runtime using Vitest by mocking NextResponse.next() and NextResponse.redirect(), which resolves environment mismatches and enables seamless middleware integration testing in jsdom.

Why does Vitest throw a Headers instance mismatch error when importing Next.js middleware?▼

Vitest throws a Headers instance mismatch error when importing Next.js middleware because the jsdom environment and the edge runtime use different Headers class implementations, requiring a mock to bypass the runtime environment mismatch.

Does mocking NextResponse in Vitest affect the testability of cookies and headers in middleware?▼

Mocking NextResponse in Vitest does not affect the testability of cookies and headers; it specifically bypasses environment mismatches while preserving the ability to test status, headers, and cookies without altering the core NextRequest object.

Related Skills

Explore More Software Engineering Skills→
TitoPrauseeTitoPrausee

vitest-monorepo-setup

Configure Vitest test infrastructure for npm and Bun workspace monorepos.

Community
Intermediate
jacob-balslevjacob-balslev
1

middleware-patterns

Design Next.js middleware patterns for Edge Runtime request preprocessing.

Community
Intermediate
akaiHuangakaiHuang

frontend-testing

Generate Vitest and React Testing Library tests for Dify frontend components, hooks, and utilities.

Community
Intermediate
rahmatullahbossrahmatullahboss

playwright

Test Next.js applications with Playwright for reliable end-to-end coverage.

Community
Advanced