Testing Applications with new Twitter API ver 1.1


We are migrating our Application from Twitter API ver1.0 to ver1.1.
I am having a question about Application testing with Twitter API new version.

Our application reads twitter text messages from the API without using OAuth so far and
from the Twitter API ver1.1 it must be authenicated before reading twitter text messages.
So we are modifying our Application to perform OAuth authenication before reading text messages…

I am wondering how to test the Application for the new API…??
As old API is supported until March of the next year how can I find that Application works
properly with the new Twitter API after it is modified for the new API??

Your answer is greatly appreciated…