I just entered the test result for Firefox 50 and Chrome 53 for your
test. I suggest 2 improvements.
Right now, only Firefox supports 'writing-mode: sideways-lr' and
'writing-mode: sideways-rl'. If the reference file also uses <div
style="writing-mode:sideways-rl"> and <div
style="writing-mode:sideways-lr"> (which is the tested feature of the
test), then browsers which do not support sideways-* writing-modes will
"pass" (false positive) your test. (This is the case with Chrome 53 and
with Edge 13 too.) In order to work around this, I suggest to create an
image of the expected results and use a textual description for the
pass/fail conditions: we have done this in about 16 tests.
... although these 2 tests did not use Hebrew and Arabic characters like
you did with your text-orientation-upright-directionality-001 test.
Interestingly, Firefox 47 passes text-orientation-upright-slr-017 and
text-orientation-upright-srl-018 but fails your
text-orientation-upright-directionality-001 test. So, this is a good