time-mock

Easily manipulate and mock out time in your tests

time-mock

Easily manipulate and mock out time in your tests

Let's say you have a simple time module that collects an array of timestamps every second.

// ./fixtures/time.js 
var setTimeout = require("timers").setTimeout
var now = require("date-now")
 
module.exports = function () {
    var items = []
 
    loop()
 
    return peek
 
    function peek() {
        return items
    }
 
    function loop() {
        items.push(now())
 
        setTimeout(loop, 1000)
    }
}

It uses require("timers").setTimeout and require("date-now") so that it's not hardcoded to time based global state.

We can then simply mock these things out using mock

var mock = require("mock")
var assert = require("assert")
 
var Timer = require("../index")
 
// Pass starting time to Timer 
var timer = Timer(0)
 
// Pass mocked setTimeout and Date.now functions to your module 
var time = mock("./fixtures/time", {
    timers: {
        setTimeout: timer.setTimeout
    }
    , "date-now": timer.now
}, require)
 
var t = time()
 
console.log("#1", t())
assert.deepEqual(t(), [ 0 ])
 
timer.advance(500)
 
console.log("#2", t())
assert.deepEqual(t(), [ 0 ])
 
timer.advance(500)
 
console.log("#3", t())
assert.deepEqual(t(), [ 0, 1000 ])
 
timer.advance(2000)
 
console.log("#4", t())
assert.deepEqual(t(), [ 0, 1000, 2000, 3000 ])
 
timer.advance(4999)
 
console.log("#5", t())
assert.deepEqual(t(), [ 0, 1000, 2000, 3000, 4000, 5000, 6000, 7000 ])

Timer basically allows you to create simple mockable functions for setTimeout and Date.now. You can then call timer.advance(delta) to make time move forward.

This is awesome for unit tests when you don't want your tests to be slow based on the fact that they have to wait for timeouts.

npm install time-mock

  • Raynos