Question: `document.cookie` is like a string, but it is not a string. To quote the example from the [Mozilla doc](https://developer.mozilla.org/En/Document.cookie):

```
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?**

Answer: 
This implementation allows overwriting cookies, and adds `document.clearCookies()`

```
(function (document) {
    var cookies = {};
    document.__defineGetter__('cookie', function () {
        var output = [];
        for (var cookieName in cookies) {
            output.push(cookieName + "=" + cookies[cookieName]);
        }
        return output.join(";");
    });
    document.__defineSetter__('cookie', function (s) {
        var indexOfSeparator = s.indexOf("=");
        var key = s.substr(0, indexOfSeparator);
        var value = s.substring(indexOfSeparator + 1);
        cookies[key] = value;
        return key + "=" + value;
    });
    document.clearCookies = function () {
        cookies = {};
    };
})(document);

```
Personally i was unable to hijack the document object.
A simple solution which seems to work for me was the following...

At the top of my test script i define a fakeCookie object:

```
var fakeCookie = {
    cookies: [],
    set: function (k, v) {
        this.cookies[k] = v;
    },
    get: function (k) {
        return this.cookies[k];
    },
    reset: function () {
        this.cookies = [];
    }
};

```

Then in my beforeEach() i define my cookie stub. This basically intercepts calls to jQuery.cookie and (instead!) call the callback function that i have defined (see below):

```
beforeEach(function() {
    var cookieStub = sinon.stub(jQuery, "cookie", function() {
        if (arguments.length > 1) {
            fakeCookie.set(arguments[0], arguments[1]);
        }
        else {
            return fakeCookie.get(arguments[0]);
        }
    });
});

```

Any time that i get or set a cookie value it uses my fakeCookie instead of the real jQuery.cookie. It does this by looking at the number of parameters passed and deduces whether its a get/set. I literally pasted this in and it all worked straight off the bat.
Hope this helps!!