At the end of the film Insurgent, it's revealed that
the box's test was created by people who founded the city and created the faction system. The message in the box could only be opened by a divergent person.
However, we saw that numerous people took the test, and everyone who failed, died. Why was the test set up so that failing was lethal? That seems counter to the purpose of the test.
Technically not everyone that failed the test died. Tris failed the Amity test at first, and would have died had Caleb not insisted Jeanine stop the sim and give her time to recover.
This I think leads us to the answer. The test in itself wasn't designed to be fatal when someone failed a test, BUT, it could be fatal if the subject was pushed beyond their limits.
It was Jeanine's methods that were fatal and not the test.
