xv

A tiny test runner focused on simplicity and speed

$ xv ./src
src/add.test.js: 0.103ms
src/sub.test.js: 0.064ms

Extracted from lowdb (TypeScript and ESM local database). One of the fastest test runner according to this benchmark.

Install

npm install xv --save-dev

Usage

Create a test file and use Node's built-in assert module:

// 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:

{
  "scripts": {
    "test": "xv src"
  }
}

Run tests:

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

npm install ts-node --save-dev

{
  "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:

{
  "scripts": {
    "test": "tsc && xv lib"
  }
}

If you're publishing to npm, edit package.json to exclude compiled test files:

{
  "files": [
    "lib",
    "!lib/**/*.test.js",
    "!lib/**/test.js"
  ]
}

Common 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 or chokidar-cli to re-run xv when there are changes.