lab-babel

1.1.1 verified Sat Apr 25 auth: no javascript maintenance

A transform for the lab test framework that enables testing of ES6/JSX modules transpiled with Babel, including code coverage and proper source maps. Current version: 1.1.1 (stable, low activity). This package integrates with lab's -T option to automatically transpile .js, .jsx, .es, and .es6 files (excluding node_modules) using Babel, preserving source maps for accurate error line numbers. Key differentiator: legacy dependency on babel-core (>=4.x.x); not intended for Babel 6+ without manual preset configuration (babel-preset-es2015). Not actively maintained; consider modern alternatives like @babel/register or ts-node.

Common errors

error Error: Cannot find module 'babel-core' ↓

cause Missing peer dependency babel-core required by lab-babel.

fix

npm install --save-dev babel-core

error Error: Cannot find module 'babel-preset-es2015' ↓

cause Missing Babel preset when using Babel 6+.

fix

npm install --save-dev babel-preset-es2015 and ensure .babelrc or package.json babel field includes 'presets': ['es2015']

error SyntaxError: Unexpected token import (or arrow functions) at runtime ↓

cause lab-babel not applied because -T flag missing or incorrect path.

fix

Use: lab -T node_modules/lab-babel (full path). Ensure tests are .js, .jsx, .es, or .es6 files.

Warnings

deprecated babel-core is deprecated in favor of @babel/core (Babel 7+). lab-babel only works with babel-core >=4.x.x and <7.x.x. For Babel 7+, use @babel/register or lab's built-in transform. ↓

fix Use @babel/register: npm install --save-dev @babel/core @babel/register @babel/preset-env; lab -T node_modules/@babel/register

gotcha lab-babel requires babel-core as a peer dependency. If babel-core is not installed, lab will silently skip transpilation without error. ↓

fix Install babel-core: npm install --save-dev babel-core

gotcha Only modules outside node_modules with extensions .js, .jsx, .es, .es6 are transpiled. Files in node_modules or with other extensions are ignored. ↓

fix Ensure your test files are in the project root directory (not in node_modules) and use one of the supported extensions.

deprecated Babel 6 requires explicit preset configuration (e.g., babel-preset-es2015). Without .babelrc or package.json babel section, transpilation fails silently. ↓

fix Create a .babelrc file with: { "presets": ["es2015"] } or install and configure babel-preset-env.

Install

npm install lab-babel

yarn add lab-babel

pnpm add lab-babel

Imports

lab-babel (transform)
wrong
```
npm install --save-dev lab-babel && lab -T lab-babel (relative path missing)
```
correct
```
lab -T node_modules/lab-babel
```
Use the full path node_modules/lab-babel when specifying the -T option to lab. The package provides no JS exports; it's used as a CLI transform.

babel-core

wrong

import babel from '@babel/core' (wrong package name for babel-core)

correct

const babel = require('babel-core')

lab-babel depends on babel-core >=4.x.x, not @babel/core. Use CommonJS require.

lab (test framework)

wrong

import { script } from 'lab' (lab is CJS, not ESM)

correct

const Lab = require('lab'); const lab = exports.lab = Lab.script()

lab is a CommonJS module. The lab-babel transform does not change lab's API.

Quickstart

Install lab-babel with babel-core and es2015 preset, configure .babelrc, write a trivial ES6 test using arrow functions, and run with lab's transform option.

npm install --save-dev lab babel-core babel-preset-es2015 lab-babel
echo '{"presets":["es2015"]}' > .babelrc
# test file: test/example.js
const Lab = require('lab');
const lab = exports.lab = Lab.script();
const Code = require('code');
lab.test('transpiled ES6', (done) => {
  const fn = (x) => x * 2;
  Code.expect(fn(5)).to.equal(10);
  done();
});
# run with: npx lab -T node_modules/lab-babel -t 100 -S