That looks tight.

You should be able to figure out how to simulate a total brake failure. Perhaps if you have Tektro levers with a release button, see what happens when you release the button.

I'm doubting it will cause a crash. Probably more like unexpected braking (which you may be able to pedal through).

However, the bike will likely also be generally unrideable without the brake cable. Thus you'll be hunting for some method to keep it locked open if you have broken cable and need to keep riding.

Have you used the GP 4 Season tires? I have a rear on one bike (23mm or 25mm) that is looking mighty bald, quicker than I expected, maybe around 2000 miles or so. I'm not sure how many punctures I've gotten. Nothing too unexpected so flat protection seems to be fine, but wear is short.