Written and oral board exams. Still a process rife with favoritism despite all of those controls because accountability of middle and upper management does not exist.
You promote when you meet minimum requirements if you'd like.
Testing and interview process for promotions
Take a long to get promoted here
Extensive but fair for first two levels of promotion
There was none, for any reason, ever.
You can promote if you are a good test taker. The process does not find true good leaders and higher ups are chosen by who they know, not what they have done.