Yup. I'm not sure what I was thinking, your simplified version is better. Also, adding a distribution is the right way. Also, no need to re-seed, only one seed is fine.

200 is not necessary, just a number that came to mind. Feel free to suggest something different.

I added a test for inequality, too. After I hear back from you about `std::string`, I'll make another pull request.

Oh yeah, I removed all the `const`s that I could. Two are required, though: the suite name and the return from `guid_null ()`.