The approved/video/video_008.htm test fails with WebKit nightly build r70732 run in Safari 5.0.x.
NOTE: The test takes a while to run (a few seconds), so be patient for the "Waiting..." message to disappear.
http://test.w3.org/html/tests/approved/video/video_008.htm is also bogus (see https://bugs.webkit.org/show_bug.cgi?id=48590).
It sets up the <video> element with <source> elements with a 'type' attribute set to "application/octet-stream":
<video id="video0" autoplay onplay="do_play(event);">
<source src="http://media.w3.org/2010/05/video/movie_300.mp4" type="application/octet-stream">
<source src="http://media.w3.org/2010/05/video/movie_5.mp4" type="application/octet-stream" media="all">
Your browser does not support media elements.
and it fails unless the the first <source> element is chosen. However, the spec says:
The canPlayType(type) method must return the empty string if type is a type that
the user agent knows it cannot render or is the type "application/octet-stream"
where the empty string is defined as "a negative response".
If there's a bug in the test, this should be reported against the test suite.