Unit Testing & Tests

[KelSolaar]

As discussed with @michdolan just 5 minutes ago, the codebase is growing, maturing and stabilising thus we should start looking at implementing some unit testing or general tests at least to protect the functionality.

At the moment, I periodically uses and launch the modules where I purposely put a __main__ clause. Maybe we could start there and turn those sections into tests and verify their output: