Testing the installer

[Ludovic Courtès]

Hello Guix!

One of the lessons from the 1.0.0 screw-up was that we should test the
graphical installer itself:

  https://guix.gnu.org/blog/2019/gnu-guix-1.0.1-released/

I think we should try to do that before the next release; not doing it
means testing by hand, which also takes a lot of time.

One idea that I had was that we could change the installer so that it
listens for connections on some pre-defined Unix-domain socket.  When it
gets a connection, it would perform a dialog with its client: sent it a
summary of the current form, wait for its choice, and so on.  The forms
would thus be unavailable from the keyboard: essentially ‘run-form’
calls would be replaced by ‘draw-form’ calls in that mode.

Our test infrastructure would thus connect (from a marionette) to the
installer and participate in that dialog.  It could even take a QEMU
screenshot at each step.

How does that sound?  Am I overlooking things?

I guess the difficulty will be to represent questions and answers.

Ludo’.