This is that part

Do the same test twice

Master the Propulsion Gel

Master the Repulsion Gel

Stand in a defective turret detector

Break the rules in Test Chamber 07

Complete the first Hard-Light Surfaces test

Reunite with GLaDOS

Complete all test chambers in the Excursion Funnels co-op course

Complete all test chambers in the Hard-Light Surfaces co-op course

Complete all test chambers in the Team Building co-op course

Kill the Pentagon thief before it can steal your load-out.

Kill 10 enemies in a row using akimbo weapons in Single Player or Special Ops.