In the example I have in mind, a Tentacruel with ridiculously low HP (like 1 or 2%) used Rapid Spin on a Ferrothorn.
Obviously the Tentacruel will faint from Iron Barbs, however since it fainted 'at the same time' as using Rapid Spin, will the move still clear the field?
That is, does one have to survive through to the end of the turn or something for the move to actually work?