Thanks for explaining that. I was actually aiming to describe code coverage in my previous comment, but completely overshot that and went to fuzzing instead, lol.

I just found https://coverage.nodejs.org/, which you're probably already aware of. Apparently it uses istanbul for JS coverage and gcov for V8.

Also, https://github.com/nodejs/node/blob/master/CONTRIBUTING.md#s... says that `make test` runs tests, presumably from https://github.com/nodejs/node/tree/master/test. Thinking about it, if Node.js' tests pass running under QEMU usermode, that should be good evidence that QEMU usermode is working too, right?

Looking further afield, I wonder if running tests from other large projects - Qt comes to mind, although you could also be utterly insane and try GCC/LLVM xD - could be used to exercise QEMU.

As an aside, I'm very curious to learn what QEMU's corner cases are, if just so that if I want to do horrible things in ELF files one day I know what won't work. :P