I wonder how well it's been verified.

This is a really big deal. Verifying a core is hard, and if the repo doesn't come with a testbench, I'm very suspicious.

Even if it does I'm suspicious. The open source RISC-V verification systems are not very good at the moment:

* riscv-arch-tests: ok, but a very low bar. They don't even test combinations of instructions so no hazards etc. * riscv-test: decent but they're hand-written directed tests so they aren't going to get great coverage * TestRig: this is better - random instructions directly compared against the Sail model, but it's still fairly basic - the instructions are completely random so you're unlikely to cover lots of things. Also it requires some setup so they may not have ran it.

The commercial options are much better but I doubt they paid for them.

See https://github.com/Wren6991/Hazard3/tree/stable/test for the test harnesses used. I wonder if they did release all they used there.