My copyright assignment is complete. Here is the patch to add tests,
signed from the same master key I used to sign the agreement:
D148 50A5 E6B1 45AE CD83  7983 16B9 CFB2 30B1 275C

This was generated against the emacs-28 branch. There will be a merge
conflict when merged to master, but these tests can just be added as
the last tests in files-tests.el