Parameterized tests

[nemequ]

I've been thinking about how to integrate µnit in Squash. Squash is an interesting case because it has many plugins, each of which contain 1 or more codec, each of which operates at 1 or more different compression level. We currently only test each codec at the default level, but it would be nice to test them all.

Parameterized tests would let us support use cases like this in a fairly clean way. Allowing callbacks to generate a list of parameter values would make things a lot cleaner for some users (including Squash). The API is going to require some thought, but I think it would be worth the effort.