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. One of the fastest test runner according to this benchmark.

Why?

With so many existing alternatives, why another test runner?

I wanted and needed something dead simple. Usually test runner/frameworks require to read multi-page documentation, hide logs and transform errors, can have complex configuration to support a wide variety of cases.

xv takes the opposite approach and makes you productive faster by being simpler. In fact, the complete documentation about xv fits this page and its code is only ~80 lines. Give it a try.

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.