Recording a video for the test case requires an ffmpeg package. To install this, you need to execute the following command in the Terminal (note that this command only works on a Debian-based OS):

apt-get install ffmpeg

Generating a video or screenshot requires the directory location of the log file, so if you are not saving the log in a separate log file, then do it through the --logfile option in the command line, like this:

./odoo-bin -c server.conf -i my_library --test-enable --log-file=/var/log/odoo.log