After one conversation with Petr, we have agreed that it would be great to have some URL in download.moodle.org in order to create some unit tests in core to check downloads of files both using file_get_contents() and componentlib stuff (the 2 ways officially supported in core to perform file downloads).
We have thought that we need something like this:
1) One BIG (say > 4K) html file, mixing UNIX/MAC/WIN linefeeds and including UTF-8 chars.
2) One binary file (any image file)
3) One .zip file of the previous files 1 & 2
4) One .md5 file of the previous file 3
5) One README.txt file containing all the md5 for all the files 1-4 and another info about unit tests.
With that, and leaving those files without modifications will be easy to create the proper unit tests for downloads within core.
I'll attach the test files here in some minutes.... going to generate them now.