Skip to content
/ uvu Public

uvu is an extremely fast and lightweight test runner for Node.js and the browser


Notifications You must be signed in to change notification settings


Folders and files

Last commit message
Last commit date

Latest commit


Repository files navigation

uvu is an extremely fast and lightweight test runner for Node.js and the browser
Ultimate Velocity, Unleashed

example with suites


  • Super lightweight
  • Extremely performant
  • Individually executable test files
  • Supports async/await tests
  • Supports native ES Modules
  • Browser-Compatible
  • Familiar API


$ npm install --save-dev uvu


Check out /examples for a list of working demos!

// tests/demo.js
import { test } from 'uvu';
import * as assert from 'uvu/assert';

test('Math.sqrt()', () => {, 2);, 12);, Math.SQRT2);

test('JSON', () => {
  const input = {
    foo: 'hello',
    bar: 'world'

  const output = JSON.stringify(input);

  assert.snapshot(output, `{"foo":"hello","bar":"world"}`);
  assert.equal(JSON.parse(output), input, 'matches original');

Then execute this test file:

# via `uvu` cli, for all `/tests/**` files
$ uvu -r esm tests

# via `node` directly, for file isolation
$ node -r esm tests/demo.js

Note: The -r esm is for legacy Node.js versions. Learn More

View the uvu CLI documentation


The uvu/assert module is completely optional.

In fact, you may use any assertion library, including Node's native assert module! This works because uvu relies on thrown Errors to detect failures. Implicitly, this also means that any uncaught exceptions and/or unhandled Promise rejections will result in a failure, which is what you want!


Module: uvu

View uvu API documentation

The main entry from which you will import the test or suite methods.

Module: uvu/assert

View uvu/assert API documentation

A collection of assertion methods to use within your tests. Please note that:

  • these are browser compatible
  • these are completely optional


via the /bench directory with Node v10.21.0

Below you'll find each test runner with two timing values:

  • the took ___ value is the total process execution time – from startup to termination
  • the parenthesis value ((___)) is the self-reported execution time, if known

Each test runner's stdout is printed to the console to verify all assertions pass.
Said output is excluded below for brevity.

~> "ava"   took   594ms  (  ???  )
~> "jest"  took   962ms  (356  ms)
~> "mocha" took   209ms  (  4  ms)
~> "tape"  took   122ms  (  ???  )
~> "uvu"   took    72ms  (  1.3ms)


MIT © Luke Edwards