PHPUnit test code inside catch block

I have a Symfony controller using try...catch. I use phpunit to test my application. I have searched but havent found a way how to test the code inside a catch exception. How can I force php unit to pretend that something went wrong and enters the catch block and test this as well?

ie:

 try {
      $foo = 1;
     } catch (\Exception $ex) {
        $mail = new Mail();
        $mail->sendMail();
        return new Response();
    }

How can I tell phpunit to throw an \Exception so it will test code inside catch block of above?