groundhog-day

groundhog-day is a wrapper around Date.now() with real and fake implementations. The real implementation returns the current time, the fake implementation returns a fixed time (defaults to Groundhog day). Use the real implementation in your production code, but inject the fake implementation in tests for predictable results.

TL;DR

1. Use a fake clock in tests

const Server = require('../server')
const request = require('request')
const clock = require('groundhog-day').fake()
const assert = require('assert')

describe('Server', () => {

  let server

  before(done => {
    server = new Server(clock)
    server.start(done)
  })

  after(done => {
    server.stop(done)
  })

  it('should set last modified header', done => {
    request.get('http://localhost/demo', (err, res, body) => {
      assert.ok(err)
      assert.equal(res.headers['last-modified'], 'Tue, 2 Feb 2016 11:00:00 GMT')  // Groundhog Day
    })
  })
})

2. Use a real clock in production

const Server = require('./server')
const clock = require('groundhog-day').real()
new Server(clock).start(err => {
    if (err) process.exit(1)
    console.log('Listening')
})

Fixing Time

You can configure the fixed time returned by the fake clock in any of the following ways:

By specifying the number of milliseconds

const clock = require('groundhog-day').fake()
clock.fix(1469563181761)

By specifying a date instance

const clock = require('groundhog-day').fake()
clock.fix(new Date(1469563181761))

By specifying a date string

const clock = require('groundhog-day').fake()
clock.fix(new Date('2016-07-26T19:59:41.761Z'))