Can you 3 star a base without destroying a tesla that isn't triggered?
Yes it is necessary to destroy all teslas.
According to the wiki
The only exception to this rule is that Hidden Teslas will reveal themselves once a base has incurred at least 51% damage, as they must be destroyed (along with all other buildings) in order to achieve 3 stars.
I tried the hiding the hidden tesla strategy, it pops up automatically after your base is destroyed by a certain amount. the only good thing about doing this is that the attacker might not have enough time to get to the hidden tesla