Since I have gone through this training, and have used it as well......."Train for the worst, hope for the best".
No, I am not saying to think "sweet thoughts and butterflies" lest someone comes back with a remark.
Sometimes it is, at 200', "what would you do if the rope broke right now?". If they hesitate, and conditions allow, yank the release and state, "rope break, now what?".
Again, throw it at them, see what they do.

I have had students throw up their hands and say, "your ship". If I think we have margin, I will put my hands on their shoulders and say, "so we go down together, what do you do next?".

The goal is not to prove I am better.
The goal is not to scare the student.
The goal is not to chase a student off.

The goal is to see what a student will do under pressure while someone else can successfully end the flight. At some point, an instructor has to sign off a student (actually they don't "have to", there are some students that should find something else to do), better to have some clue what said student will do when crap happens.

A bit of stress in a semi controlled situation is a decent barometer of what may happen down the road.

Heck, I have pulled the release, during BFR's/field checks, at 1800'AGL and said, "rope break".
Curious to see the response. Situational awareness is major here.

At the end of any of these flights above, discuss what went well, what may need work. Also find out what the student/testee saw or thought.
Work from there.