Cookie is small information stored in text file on user’s
hard drive by web server. This information is later used by
web browser to retrieve information from that machine.
Generally cookie contains personalized user data or
information that is used to communicate between different
web pages.
   
 Test the application by enabling or disabling the cookies
in your browser options. Test if the cookies are encrypted
before writing to user machine. If you are testing the
session cookies (i.e. cookies expire after the sessions
ends) check for login sessions and user stats after session
end. Check effect on application security by deleting the
cookies.

The main purpose of cookies is to identify users and 
possibly prepare customized Web pages for them. When you 
enter a Web site using cookies, you may be asked to fill 
out a form providing such information as your name and 
interests. This information is packaged into a cookie and 
sent to your Web browser which stores it for later use

1 – check information is cookie is encrypted or not
2 – check to run application disable cookie from I.E 
Property
3 – Check cookie will expire after session is expire
4 – Check if the browser is close without Logout , cookie 
is expire or not