Measuring tension of a rope constraint with a restitution of 0?

So I'm making a game where the main feature is a grapple hook that emulates the one from the Just Cause franchise. Players are able to tether two objects together with a rope constraint. I want the rope to have a breaking point, but for that to work I need to be able to measure the tension of the rope.

The rope has a restitution of 0, which means it's non-elastic so I can't measure to see if the distance between the two attachments of the constraint is slightly greater than the rope length.

Does anyone have any ideas on how I could make a rope breakable with enough force? Maybe I could barely adjust the restitution so the rope has some give that I can measure?