Make clean tests

[Mesabloo]

At the moment, tests rely on some basic naming conventions for test files.
It would be great to write a small test engine which automatically fetches files in some folder, tries to parse + typecheck + codegen those files, and depending on the name of the file (for example if it begins with "error_" then it is expected that some step fails. We can make this better by writing which error is supposed to happen, something like "error_tc" for a typechecking error etc)
I think this can be done really easily, while still keeping some useful information like fails etc