went through it big time-not a nice situation.
i worked for a government agency and the 'normal course' to move into managment (in my field) was to work your way up to a certain classification (minimum of 4 1/2 years) to meet the criteria when testing came around. people would usualy take the test at least twice before they scored high enough to qualify for a hiring interview (and the tests might only be given every few years depending on weather there were vacancies or hiring freezes).
i did my 4 1/2 years and the next test was announced a couple of years later (and it had been YEARS since one had been given so i had co-workers who had massive seniority over me and had taken the test at least once before so they knew what to expect and how to prep for it). i went in and while i thought i did 'o.k' i did'nt think i had aced it by any means (it happened to fall about 2 weeks after i delivered my first child-i had been off on maternity leave for over a month, my brain felt like it was fogged from hormones and sleep deprivation-not to mention i was tightly squeezed into the only suit i could get my fat post partum body into, which of course i was sweating like a pig in

). imagine my suprise when i got notification that my combined oral and written tests ranked me as #2 on a list of over 200).
to say my co-workers were jealous is a bit of an understatement-people i had worked beside and got along great with were downright hostile. i endured nasty comments about how i had somehow managed to cheat on the test or knew someone who knew someone...people selectivly forgot that prior to the test i had chosen to take classes (on my own time) that our employer offered in supervision, had taken 'grunt' jobs that exposed me to doing undesirable case reviews (a part of the testing criteria), had opted to work in multiple programs to get some diverse knowledge/experience under my belt (all of which they not only could have done but with their seniority if they had opted to would have bumped me from being able to).
it got even worse when i ended up supervising people i had worked beside (and then compound that by 10 when a few ultimatly did become supervisors but their technical work was required to be reviewed by me before assigning it to our line staff-and our supervisor required errors be documented and reported to her-not a position you want to be in with an animosity driven peer

).
suffice it to say-i'm glad to be 'out of there'.