Is it possible to mock document.cookie in JavaScript?

javascript, unit-testing

Solution

You could create an object with a `cookie` setter and getter. Here is a very simple implementation:

var mock = {
    value_: '', 

    get cookie() {
        return this.value_;
    },

    set cookie(value) {
        this.value_ += value + ';';
    }
};

Might not work in all browsers though (especially IE). Update: It only works in browsers supporting ECMAScript 5!

More about getter and setters.

mock.cookie = "name=oeschger";
mock.cookie = "favorite_food=tripe";
alert(mock.cookie);
// displays: name=oeschger;favorite_food=tripe;

DEMO

Problem

`document.cookie` is like a string, but it is not a string. To quote the example from the Mozilla doc: ``` document.cookie = "name=oeschger"; document.cookie = "favorite_food=tripe"; alert(document.cookie); // displays: name=oeschger;favorite_food=tripe ``` If you tried to make a mock cookie using only a string, you would not get the same results: ``` var mockCookie = ""; mockCookie = "name=oeschger"; mockCookie = "favorite_food=tripe"; alert(mockCookie); // displays: favorite_food=tripe ``` So, if you wanted to unit test a module that operates on the cookie, and if you wanted to use a mock cookie for those tests, could you? How?

Original source