denude

All that is hidden shall be revealed

Although testing private members is considered an antipattern, sometimes you really, really need to. Denude makes it easy to require functions and variables from the top scope of a module.

Usage

Module you want to test:

const { format } = require('util')


let prefix = 'Hello, '

function greet(name) {
  return format(`${prefix}%s!`, name)
}

function helloWorld() {
  return greet('World')
}

module.exports = { greet, helloWorld }

Test file:

const denude = require('denude')
const { helloWorld, greet: publicGreet } = denude('./module') // public parts
const { format, prefix, greet } = denude('./module?private') // private parts

console.log(greet === publicGreet) // true
console.log(helloWorld()) // Hello, World!

Notice that denude works independently from require. It means that require('./module') and denude('./module') will return different instances of all the members of the module:

const required = require('./module')
const publicDenude = denude('./module')
const privateDenude = denude('./module?private')

console.log(required.greet === publicDenude.greet) // false
console.log(privateDenude.greet === publicDenude.greet) // true

Overriding require

You can use require('denude/register') to patch the native require globally. After that, any require that is passed a path with the ?private prefix will return the private members instead of the exports.

Example:

require('denude/register')

const helloWorld = require('./module') // public parts
const { format, prefix, greet } = require('./module?private') // private parts

This technique is useful with testing frameworks like mocha and ava that allow requiring modules on run:

mocha --require denude/register test

License

ISC