The tests are not extensive. Just hand written assembly code testing one thing at a time AFAIK. As someone who used to lead ASIC verification projects for a living, I expected a lot more at a minimum.
I don't know what the Chisel stuff checks. Chisel doesn't do anything at the simulation stage I believe.
I guess if you are just playing around with CPU designs, you can use this stuff.
I would never sign off on going to tape out with just this stuff though. Apparently they've taped out over 11 times though!
You want to run the RTL and compare against the ISA simulator? I think you're on your own...