Both patches were only "lightly" tested, i.e. by C-x C-e'ing every
function and test, then calling ert-run-tests-interactively; AFAICT the
tests pass[1].  Haven't run a full 'make check' yet (M-: insert-excuse
'battery); I don't think anything broke when Stefan committed the fix to
font-lock-prepend-text-property though.

Still pretty new to this, so let me know if I messed up anything
(e.g. commit message format, conventions when adding files, functions or
tests).

Thank you for your time.



[1] Although running 'make lisp/font-lock-tests' in the test/ folder
    fails on the append test.  Could it be that the Makefile runs the
    tests against the old font-lock.el that is installed on my system,
    rather than the new one in my repository?  I took a look at the
    test_template in test/Makefile, but I could not understand what the
    machinery loads at a glance.