Our testing is public, and not particularly long or stressful. We subscribe to the idea that you're not really testing. When you're invited to test, you've already demonstrated clearly, on multiple occassions, that you can meet or exceed all the expectations of the upcoming rank.
Testing is only semi-standardized.
Poomse - You're expected to perform the form required for your rank, and depending on rank and time available, one or more (even all...) of those from the lower ranks.
Free sparring and self defense - Again, there are minimum requirements, but when time allows, students are given the opportunity to demonstrate skills beyond the minimum. Sparring against multiple opponents, for example.
Breaking - There is a required break for each rank, but how many boards depends on the student. I've never done a single board break, and starting with 3rd geup I've done multiple station breaks.
The idea is to give the student a chance to demonstrate what they've learned and put on a bit of a show.