http://www.w3.org/TR/cssom/#the-cssrule-interface const unsigned short NAMESPACE_RULE = 10; The test case in Shepherd shows that Webkit browsers don't have the property NAMESPACE_RULE
Furthermore, we have WEBKIT_REGION_RULE with value 10 now.
How does WEBKIT_REGION_RULE relate to REGION_STYLE_RULE? See also: http://wiki.csswg.org/spec/cssom-constants
WEBKIT_REGION_RULE is REGION_STYLE_RULE which should be 16, as Ed's cssom-constants link specifies.
I have created the WebKit bug https://bugs.webkit.org/show_bug.cgi?id=89421 for the value change of WEBKIT_REGION_RULE from 10 to 16.
I am not sure whether anything further is required but Safari 15.6 on macOS 12.5 do pass all 7 tests: Link - http://test.csswg.org/shepherd/repository/b5702ea054bc323792c6c9db062224c05499ae85/cssom-1/cssstylerule.html Matching all other browsers (Chrome Canary 106 and Firefox Nightly 104). Is something else needed here? Thanks!
> CSSRule.NAMESPACE_RULE < 10 > CSSRule.WEBKIT_REGION_RULE < undefined