Implement a cram tests workflow

[pitag-ha]

Currently we don't have any tests (at least no "reasonable" test). @panglesd has already implemented a very nice CI to test if the whole installation works, which we should merge asap.

Apart form that, it might also be nice to have some finer-grained end-to-end testing, such as a cram test workflow. In our case, we can't simply use dune cram tests since we want to test the installer in an environment in which dune doesn't necessarily exist. Still, it would be nice to have a cram test workflow, for example to test logging and error reporting. What do you think?

[pitag-ha]

I was just wondering: do we still need this or can we close this issue? I haven't followed up very much on our tests, but from what I understand it's already quite complete, isn't it? @panglesd, do you have an opinion on if we still need this?

[panglesd]

The tests mechanism is I think very nice but tedious to use.

I think that at some point we should improve the usability and why not add a "cram test" possibility, to stop having to test string equalities in the bash syntax.