how to generate transactions using braintree gateway

Hi all,
I am sassy rails app for testing transaction.

I have installed the sassy from git clone git://github.com/maccman/saasy.git
when I launch the server
script/server
I am able to signup.
but when I go to billing menu after changing the plan, it says no
transaction so far

How to create transaction?
please help

Thanks
Nagaraj