Xv

A tiny (~80 lines of TypeScript) 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

If you've used other test runners, you probably have spent a significant amount of time reading docs, configuring, maintaining and debugging them.

By being extremely simple, xv gets out of your way and lets you be productive faster. In fact, the whole project documentation fits in this page ;)

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.