I had one done about 2 weeks ago by a PhD researcher - I don't get the official results until her supervisor returns - I had volunteered for one of their studies in 2001 so they will have that to compare - this test was also part of a study so I had to sign consent forms, but it was free.
I wasn't feeling too bad that day - though only had about 5 hours sleep and had vaporized medical marijuana in the morning for mild nausea - I told her before we started that I was pretty sure the results would be different if I had of being feeling worse as my experience with brain fog is totally correlated with symptom intensity - so in weird a way, I kind of felt like I was wasting our time.
It took a couple of hours so was taxing mentally just from an endurance viewpoint - during a couple of the tests she said that I had 'reached the ceiling', meaning that my memory was very good - I'll be interested to see the results in a few weeks, but not really anticipating any significant changes form 2001 just based on how I was feeling that day.
If there are specific cognitive tests for m.e. I'd like to ask if they were administered.