actually that it is in the test cases instead of the readme makes it seem worse to me, after all the readme is not addressed to anyone in particular, they needed examples of things someone might do and they used popular videos (that happened to be copyrighted) as those examples.

But anyone running the test cases that does not have rights to those videos will have infringed, and then of course youtube-dl must also run their own test cases and we know they don't have rights to the videos.