Test if each value (auto, alphabetic and under) works. Auto defaults to alphabetic, so they should look the same, that is, the horizontal line should cross the 'p' letter in the word 'ipsum'. Under should not cross the 'p' letter. Bugzilla link: http://webkit.org/b/102795.

auto lorem ipsum
alphabetic lorem ipsum
under lorem ipsum
auto lorem ipsum under lorem ipsum alphabetic lorem ipsum