Unit tests

[c-dilks]

Currently we just test using the examples, but we will eventually have a lot of algorithms. It would be nice to unit test them.

Meson has some support for this, where we could use the example executables, but perhaps we need a more generalized executable to cover all the algorithms. We also need to check the output is correct.

We could use a common testing framework such as catch2 or gtest; feed an algorithm some manually-made banks, then check if the output is as expected.

Any additional dependencies that are needed for unit testing should be optional, since not all users will be interested in running them (rather, that is the job of the CI and developers).