It appears that spellcheck / auto correction tests don't work at all in WebKit2. We need to make them working in WebKit2.
WebKitTestRunner doesn't enable spell checking settings for Mac. I disabled this code as Mac hadn't compiled API to control spell checking - WKTextChecker.h/cpp. See https://trac.webkit.org/browser/trunk/Tools/WebKitTestRunner/TestController.cpp#L591
Please omit this comment if Mac enables the spell checking by default.
FWIW, platform/mac/editing/spelling/delete-autocorrected-word-2.html passed for me on Yosemite in WK2.
I did not investigate any further. It could be that this test works now, or that all of them work, or even that this test fails on both WK1 and WK2, and has wring results checked in.
My patch in https://bugs.webkit.org/show_bug.cgi?id=190764 adds a new mechanism for making spelling dots be drawn in WK2 tests.