Introduce automated UI testing based on asciinema

[hartwork]

This will prevent the next case of #102 right in the pull request introducing the regression.

This took quite a while to build, I ran into many interesting walls in the process and now finally have it working. Happy to answer questions about it.

[edgar-bonet]

Automated visual inspection in CI? Wow! That's awesome! I find this really great, but at the same time I am a bit worried this could cause some friction for contributions that legitimately change the rendering. I understand in such a case one could push the change, wait for the CI to fail, download the generated artifacts, commit the actual images as the expected ones, and push again. It would be a bit cumbersome though.

Could one instead just run record.sh to get the expected images? I can't find the agg command on the Ubuntu repos, is there an alternative?

[hartwork]

Automated visual inspection in CI? Wow! That's awesome!

@edgar-bonet glad you like the idea!

I find this really great, but at the same time I am a bit worried this could cause some friction for contributions that legitimately change the rendering. I understand in such a case one could push the change, wait for the CI to fail, download the generated artifacts, commit the actual images as the expected ones, and push again. It would be a bit cumbersome though. Could one instead just run record.sh to get the expected images?

Yes!

The fail-and-download approach would work, but I would personally see it as a fallback, as a second option, not the primary way, at least that was not intended. What I did locally to produce fresh images was basically this:

cd recordings/
./record.sh
for i in actual-*.png ; do cp ${i} ${i/actual/expected}; done
for i in expected-*.png ; do zopflipng -y ${i} ${i}; done  # https://github.com/google/zopfli
git add expected-*.png

I can make that a second script sync.sh or so if that changes something. Maybe without the git addto not interfere with the developers workflow. What do you think?

I can't find the agg command on the Ubuntu repos, is there an alternative?

agg is https://github.com/asciinema/agg and Gentoo doesn't have a package either. (It does have x11-libs/agg but that's something else). What I did and considered okay at least for myself was…

cargo install --git https://github.com/asciinema/agg
export PATH="${PATH}:${HOME}/.cargo/bin"

…and then command agg is readily available with a version fully compiled from source.

[edgar-bonet]

LGTM.