I am new to CODEIGNITER framework and i have a problem to check whether is set session['username'] 

in "php" I would just do : 

```
if( is set ($_SESSION['username'])){
        $username = $_SESSION['username'];
        //...more code here
    }  else {
        //more code here
    }

```

But i don't know how to test that in this framework.
Thanks to everyone willing to help me!