How to know if exists a shiro session from a browser perspective ?

[Cristiano Gavião]

Hi,

I'm developing a integration test for my application using selenium2 + 
webdriver.

At code I test if the user is authenticated using: 
subject.isAuthenticated()when the home page is called. If he is not, 
then he is forwarded for the login page.

I would like to simulate such situation. So anyone knows if there is a 
way to know (from a browser perspective) if there is or not a shiro 
session ?

thanks

Cristiano