Server :: CentOS 5.6 Patch Version Control?

I have this project at work. We are a MS Windows shop, and I am "supposed" to be the linux expert, which means, linux support, it's me. I have worked with linux maintaining PCs at home with different versions of linux since 1995, jumping from Slackware to Ubuntu.

Now, I have two CentOS 5.6 boxes, and I need to control the patching process. the boxes are hosting an application which we don't manage. So. one box in production, one box in development. The idea is that the box in development wil use yum in a standard way and download whatever patches are needed, and the application is tested. When the testing is done (this can take minutes, hours, or days) then the production box gets patched.
The problem is that I need to garantee that exactly the same patches are applied in development and in production.

the development box downloads the patches from the internet, but the production box gets it's patches from the development box, not the internet. I have played around with making local repos on the development box and samba, or rsync the /var/yum/cache, and to change the yum.repo.d CentOS-base.repo to force the prod to go to the dev box, without success.