How do I adjudicate the logic modality of certain death regarding the Fast Friends spell?

When I cast the Fast Friends spell could I assign the afflicted target to a task that leads to a die roll that has a chance of 98% from death by falling damage without the spell ending immediately?

If the activity would result in certain death for the creature, the spell ends.

Does the task have to necessarily lead to death for the spell ending condition to take place?

How do I adjudicate death probabilities for the purpose of the duration of the Fast Friends spell?