When you first open TheBrain it immediately starts upgrading the last opened brain. I believe it used to prompt you if you wanted to upgrade.
Then if you have the brain set to sync automatically it immediately starts the sync.
If you plan on using a copy of your primary database for testing, I would suggest opening the version ofPersonalBrain you are currently using first and open the brain you plan to use. Then choke File > Utilities > Assign New Brain GUID. Then start TheBrain 7 and let it open the copied brain and do it's thing.