metamask-extension/test/unit/app/nodeify-test.js

const assert = require('assert')
const nodeify = require('../../../app/scripts/lib/nodeify')

describe('nodeify', function () {
  const obj = {
    foo: 'bar',
    promiseFunc: function (a) {
      const solution = this.foo + a
      return Promise.resolve(solution)
    },
  }

  it('should retain original context', function (done) {
    const nodified = nodeify(obj.promiseFunc, obj)
    nodified('baz', function (err, res) {
      if (!err) {
        assert.equal(res, 'barbaz')
        done()
      } else {
        done(new Error(err.toString()))
      }
    })
  })

  it('no callback - should allow the last argument to not be a function', function (done) {
    const nodified = nodeify(obj.promiseFunc, obj)
    try {
      nodified('baz')
      done()
    } catch (err) {
      done(new Error('should not have thrown if the last argument is not a function'))
    }
  })

  it('no callback - should asyncly throw an error if underlying function does', function (done) {
    const nodified = nodeify(async () => { throw new Error('boom!') }, obj)
    process.prependOnceListener('uncaughtException', function (err) {
      assert.ok(err, 'got expected error')
      assert.ok(err.message.includes('boom!'), 'got expected error message')
      done()
    })
    try {
      nodified('baz')
    } catch (err) {
      done(new Error('should not have thrown an error synchronously'))
    }
  })

  it('sync functions - returns value', function (done) {
    const nodified = nodeify(() => 42)
    try {
      nodified((err, result) => {
        if (err) return done(new Error(`should not have thrown any error: ${err.message}`))
        assert.equal(42, result, 'got expected result')
      })
      done()
    } catch (err) {
      done(new Error(`should not have thrown any error: ${err.message}`))
    }
  })

  it('sync functions - handles errors', function (done) {
    const nodified = nodeify(() => { throw new Error('boom!') })
    try {
      nodified((err, result) => {
        if (result) return done(new Error('should not have returned any result'))
        assert.ok(err, 'got expected error')
        assert.ok(err.message.includes('boom!'), 'got expected error message')
      })
      done()
    } catch (err) {
      done(new Error(`should not have thrown any error: ${err.message}`))
    }
  })
})