mocha-working-example-1 created by justsml - https://repl.it/@justsml/mocha-working-example-1

index.js

runTests()




function runTests() {
  const Mocha = require('mocha')
  require('sinon')
  const mocha = new Mocha()
  mocha.addFile('test.js')

  mocha.run((failures) => {
    process.on('exit', () => {
      process.exit(failures);
    })
  })
}

lib.js

// # answer:

module.exports = function promisify(fn) {
  return (...args) => {
    return new Promise((resolve, reject) => {
      fn(...args, (error, result) => {
        if (error) return reject(error)
        return resolve(result)
      })
    })
  }
}

package-lock.json

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}

test.js

require('mocha-sinon')
const expect = require('chai').expect

const lib = require('./lib.js')

const promisify = lib

const testValueFn = (value, callback) => {callback(null, value)}
const testFailFn = (callback) => {callback(new Error('Callback Fail'), null)}

describe('promisify utility', function() {
  beforeEach(function() { this.sinon.stub(console, 'log') })

  it('promisify() returns another function', function() {
    const testFn = (callback) => {callback(null, 42)}
    const testFnAsync = promisify(testFn)
    expect(testFnAsync).to.not.be.null
  })
  it('promisify()\'s return function handles callback success', function() {
    const testFn = (callback) => {callback(null, 42)}
    const testFnAsync = promisify(testFn)
    expect(testFnAsync).to.not.be.null
    expect(testFnAsync).to.not.be.null
  })
  it('promisify()\'s wrapper function returns a promise', function(done) {
    const testFn = (callback) => {callback(null, 42)}
    const testFnAsync = promisify(testFn)
    expect(testFnAsync).to.be.a('function')
    const p = testFnAsync()
    expect(p).to.be.an.instanceof(Promise)
    p.then(value => {
      expect(value).to.equal(42)
      done()
    })
    .catch(done)
  })
  it('promisify()\'s function handles Errors', function(done) {
    const testFailFnAsync = promisify(testFailFn)
    expect(testFailFnAsync).to.be.a('function')
    const p = testFailFnAsync()
    expect(p).to.be.an.instanceof(Promise)
    p.then(value => {
      done(new Error('Error Shouldn\'t result in success'))
    })
    .catch(error => {
      expect(error.message).to.equal('Callback Fail')
      done()
    })
  })
})