[](https://github.com/typicode/xv/actions/workflows/node.js.yml) [](https://packagephobia.com/result?p=xv) > A tiny test runner focused on simplicity and speed ```sh $ xv ./src src/add.test.js: 0.103ms src/sub.test.js: 0.064ms ``` _Extracted from [lowdb](https://github.com/typicode/lowdb) (TypeScript and ESM local database). One of the fastest test runner according to this [benchmark](https://github.com/icetbr/comparing-testing-libraries)._ ## Install ```sh npm install xv --save-dev ``` ## Usage Create a test file and use Node's built-in [`assert`](https://nodejs.org/api/assert.html) module: ```js // src/add.test.js import assert from 'node:assert/strict' import add from './add.js' // This is plain Node code, there's no xv API export function testAdd() { assert.equal(add(1, 2), 3) } ``` Edit `package.json`: ```json { "scripts": { "test": "xv src" } } ``` Run tests: ```sh npm test # run all test files in ./src npx xv src/add.test.js # run a single test file ``` ## Convention By default, xv will look for files named: `*.test.js`, `test.js`, `*.test.ts` and `test.ts` ## TypeScript ### With TypeScript + [ts-node](https://typestrong.org/ts-node/) ```sh npm install ts-node --save-dev ``` ```json { "scripts": { "test": "xv --loader=ts-node/esm src" } } ``` ### With TypeScript only Compile your `.ts` files using `tsc` and run `xv` on compiled `.js` files. For example, assuming your compiled files are in `lib/`, edit `package.json` to run `xv` after `tsc`: ```diff { "scripts": { "test": "tsc && xv lib" } } ``` If you're publishing to npm, edit `package.json` to exclude compiled test files: ```json { "files": [ "lib", "!lib/**/*.test.js", "!lib/**/test.js" ] } ``` ## Common JS ```js // src/add.test.js const assert = require('assert').strict; const add = require('./add') exports.testAdd = function() { assert.equal(add(1, 2), 3) } ``` ## Watch mode xv doesn't have a watch mode. If the feature is needed, it's recommended to use tools like [watchexec](https://github.com/watchexec/watchexec) or [chokidar-cli](https://github.com/open-cli-tools/chokidar-cli) to re-run xv when there are changes.