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.cursor/rules/testing.mdc

Cursor testing rule for Node.js

A Cursor `.mdc` rule can attach only when you touch tests. This variant keeps testing policy out of the always-on project rule so day-to-day edits stay quieter. This copy is written for a Node.js project. This repository is a TypeScript program on Node.js. Use ESM if the package already does, and prefer `node:` imports for built-in modules. The default test runner, when one is needed, is node:test.

The example uses a balanced, readable style, pragmatic tests, and comments only where the intent is not obvious. Open the generator to make the agent stricter, switch to test-first, quiet the comments, or pick a different file.

The example assumes TypeScript on modern Node. It does not assume Express, Fastify, or a database. Do not add a framework if the repo is a library or a small script.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: testing.mdc

---
description: "Testing rules for a Node.js repository"
globs: "**/*.{test,spec}.ts"
alwaysApply: false
---

# Testing rules

Attach these rules when editing tests in this Node.js repository.
The always-on project rule still lives in `.cursor/rules/project.mdc`. This file does not repeat it.

## Stack

This repository is a TypeScript program on Node.js. Use ESM if the package already does, and prefer `node:` imports for built-in modules. The default test runner, when one is needed, is node:test.

## Commands

- Dev: `npm run dev`
- Typecheck: `npx tsc --noEmit`
- Tests: `npm test`
- Lint: `npm run lint`

Use the script the repo already defines when it differs from the command above.

## Testing

Add or update tests when behavior changes.

Use the existing runner. If the repo has none, add a node:test file for the behavior you changed.

## Done when

- The requested behavior works.
- `npx tsc --noEmit` passes for the project, and `npm test` passes when tests exist.
- The diff stays inside the task.
- You list anything you could not run.

Add it to the project

  1. 01

    Copy a starting file

    Copy the example Cursor testing rule on this page, or open the generator if you want different testing, strictness, or comment rules.

  2. 02

    Save it at .cursor/rules/testing.mdc

    Save it at `.cursor/rules/testing.mdc` in the Node.js repo, next to the always-on project rule. Leave `alwaysApply` false so it only joins test edits.

  3. 03

    Start a fresh agent session

    Rules files are read when a session starts. A chat that is already open may still be using the old instructions.

  4. 04

    Give it one small task

    Ask for one change a Node.js agent often gets wrong, such as a function that validates its input and returns a typed error instead of throwing a string. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put Cursor testing rule in a Node.js repo?

Save it at `.cursor/rules/testing.mdc` in the Node.js repo, next to the always-on project rule. Leave `alwaysApply` false so it only joins test edits.

Which tools read this Cursor testing rule?

Cursor loads `.cursor/rules/testing.mdc` when a file matches its globs. It does not replace `project.mdc`. Keep the always-on rule for stack conventions.

What does the Node.js example assume?

The example assumes TypeScript on modern Node. It does not assume Express, Fastify, or a database. Do not add a framework if the repo is a library or a small script.

Does VibeSpell upload my repository?

No. Recipe pages are static, and the generator builds the file in your browser from the options you pick. Your source code never leaves the machine.

Other files for Node.js

Cursor testing rule for other stacks