In order to generate screenshots for the failed test cases, you need to run the server with the path of the log files. When you run the test cases along with the name of the log file, Odoo will save the screenshot of the failed test cases in the same directory. If you are not saving the log in a separate log file, then you can do it through the --logfile option in the command line.

To generate the video of the test case, Odoo uses the ffmpeg package. If you haven't installed this package in the server, then it will only save the screenshot of the failed test case. After installing the package, you will be able to see the mp4 file of the failed test case. Note that screenshots and videos are only generated for the failed test cases, so if you want to test them, you need to write a test case that fails.