Why

• User-friendly - zero-config, no API to learn, simple convention, ESM support
• Extremely lighweight - only 40 lines of code and no dependencies
• Blazingly fast - with almost zero abstractions, xv is as fast as Node
• Stable - very low maintenance
• Unix philosophy™ - do one thing well, xv is only a test runner

lowdb (local JSON database), steno (fast file writer) and other awesome projects are using xv to run tests.

Status

The project being very simple by design, there probably won't be frequent updates to the code (which is a good thing for you, unless you like Dependabot alerts and updating devDependencies). It will be updated to support latest Node releases and implement potential improvements.

tl;dr xv is maintained and used even though code updates may not be recent.

Install

npm install xv --save-dev

Usage

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

// src/add.test.js
import { strict as assert } from 'assert'

export function testAdd() {
  assert.equal(1 + 2, 3)
}

Edit package.json:

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

Run all test files:

npm test

Run a single test file:

npx xv src/add.test.js 

Convention

When provided with a directory, xv will look for files named *.test.js or test.js and run exported functions sequentially.

TypeScript

To test TypeScript code, compile your .ts files 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": "xv src"
+   "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"
  ]
}

Watch mode

xv doesn't integrate 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.