For the ground operations launch simulations at KSC (Kennedy Space Center) the tests were all hardware / software failures testing how the teams would react to those failures. Onboard failures, ground equipment failures, etc. I can't speak for the tests they ran at JSC (Johnson Space Center) but I don't personally remember any "team / crew goes berserk" tests. There was enough hardware simulated failures to test the team with.
I guess that the thought of an engineer going berserk during load / countdown / launch really didn't come up because of the process they put engineers through to get on the console for launch. There were several layers of certifications to go through:
Level 3 - GSE - Only able to go into the firing room and issue commands to Ground Support Equipment that was NOT connected to the vehicle
Level 2 - Test / Checkout - Only able to send command to equipment during the test / checkout getting the vehicle ready for launch
Level 1 - Load / Launch (for MPS / SSME / LH2 / LOX console, I suspect that APU / OMS had level 1 for loading propellants) - Able to perform any kind of tests up to and including launch
To get to each of these levels you had to go through a "standboard". First your supervisor has to give you tests on your system and assuming you passed the tests then they would essentially vouch for you for your standboard. The standboard consisted of questions from OTC (Orbiter Test Conductor), Safety, Quality control, Engineering (I am forgetting someone). The questions could literally be anything, with your supervisor stepping in to say of a question was out of bounds.
All this to say that your manager knew you and would not vouch for you if you were not mentally stable. So you wouldn't even be on console for testing.
Addendum, my cert card. You can see I was:
CMPS/CMPL (Main Propulsion System LH2 / Main Propulsion System LOX) - Level 1 - Test/Checkout/Load/Launch
CCME (Space Shuttle Main Engine Controllers) - Level 2 - Monitoring/Test/Checkout
CSME - Space Shuttle Main Engines Level 2 - Test/Checkout