If you build your own wallet you can already start using it (backup your wallet before just in case), nothing is supposed to change, then check your balance, send and receive some transaction. This would test it for existing installations where blockchain is already downloaded.

Another test would be deleting the blockchain and starting the wallet (again, don't forget to backup wallet). Then the same tests as before (balance, sending and receiving)

For those who use the  windows, linux or osx wallets we will need to wait until they are updated.

Adriano