This article explains how you can test architecture changes to your CMS instance and assumes you are already familiar with Understanding the Impact of Changes to your CMS instance.
If you do have changes in your CMS architecture you should ensure that you have sufficiently tested the update prior to synchronizing your changes to your production web server.
Test on production in Preview Mode
If the change you've made still requires a publish to synchronize to the web server (i.e. a module definition update) then you can initiate a preview session on the production web server to test how the code interacts with your new update. Note this will only work for updates that require publishing prior to synchronizing.
Temporarily Deactivate the syncing production web server
If the change you need to make will synchronize immediately with all web servers or you want to test what happens when you publish an update, you may temporarily deactivate the content sync on the production web server.
You can then publish content and make other configuration changes and synchronize those with your uat/staging environment. Deactivating the content sync on the production web server allows you to do end-to-end testing on uat/staging with the latest changes. At this point, assuming that uat/staging has the same code-base as production and your tests pass then you can be confident your update will work the same on production.
The final step is to activate the production syncing web server again and proceed to Sync Pending changes via the Detailed Sync Status report found in Reports > Details Sync Status. This will synchronize all pending changes since your production content sync was deactivated.