Fake timers are synchronous implementations of setTimeout and friends that Sinon.JS can overwrite the global functions with to allow you to more easily test code using them.

Fake timers provide a clock object to pass time, which can also be used to control Date objects created through either new Date(); or Date.now(); (if supported by the browser).

When faking timers with IE you also need sinon-ie.js, which should be loaded after sinon.js.

For standalone usage of fake timers it is recommended to use lolex package instead. It provides the same set of features and was previously extracted from Sinon.JS.

    setUp: function () {
        this.clock = sinon.useFakeTimers();

    tearDown: function () {

    "test should animate element over 500ms" : function(){
        var el = jQuery("<div></div>");

        el.animate({ height: "200px", width: "200px" });

        assertEquals("200px", el.css("height"));
        assertEquals("200px", el.css("width"));

Fake timers API

var clock = sinon.useFakeTimers();

Causes Sinon to replace the global setTimeout, clearTimeout, setInterval, clearInterval and Date with a custom implementation which is bound to the returned clock object.

Starts the clock at the UNIX epoch (timestamp of 0).

var clock = sinon.useFakeTimers(now);

As above, but rather than starting the clock with a timestamp of 0, start at the provided timestamp.

var clock = sinon.useFakeTimers([now, ]prop1, prop2, ...);

Sets the clock start timestamp and names functions to fake.

Possible functions are setTimeout, clearTimeout, setInterval, clearInterval, and Date. Can also be called without the timestamp.


Tick the clock ahead ms milliseconds.

Causes all timers scheduled within the affected time range to be called.


Restore the faked methods.

Call in e.g. tearDown.