How much can I shield/heal? (practice tool)

Hello everybody! I'm main support and I main champions like Janna, Soraka and Nami that have a lot of heals and shields. The other day I wanted to see how I could build them and get the max amount of shields possible. So I went to the practice tool and... there is no way to see it. As it is impossible to invite a friend to help you out here, I used my allied dummy and put a shield on him. And the other think that changed is the ad it has, because it had his maximun life. So I just took my friend to an enemy tower so I could lower his life and then see how much I shield. Impossible, it doesn't take any damage from towers, minions or dragons. I've been using the practice tools sometimes and it looks that it's amazing to change damage builds, because the enemy dummy shows how much damage you've dealt with last hit and crit. But it's impossible to check the shields or heals, and it would be really nice to get the max out of it.