A friend said that excess damage will spill over and hit the player, but I can't find anything to support that. I've seen 306.7:
306.7. If noncombat damage would be dealt to a player by a source controlled by an opponent, that opponent may have that source deal that damage to a planeswalker the first player controls instead. This is a redirection effect (see rule 614.9) and is subject to the normal rules for ordering replacement effects (see rule 616). The opponent chooses whether to redirect the damage as the redirection effect is applied.
but that doesn't mention excess damage.
For example, in any of the following scenarios, does the excess damage hit the player after killing the Planeswalker?
- If I hit a Planeswalker with 4 loyalty like Samut, the Tested with a 5/5 creature like Collasapede?
- If I hit a Planeswalker with 4 loyalty like Samut, the Tested with a 5/5 creature with trample like Giant Warthog?
- If I hit a Planeswalker with 4 loyalty like Samut, the Tested with an instant or sorcery that does 5 damage like Explosive Impact?