h1><a href="https://drafts.csswg.org/css-content/#alt">Mixed Alternative Text (attr() and strings) for  CSS content (previously `alt:`)</a> in pseudo-elements</h1>
<p>rendered text should be "before label after"</p>
<p>accessibility label should be "start alt-before end label start alt-after end"</p>
<button data-alt-text-before="alt-before" data-alt-text-after="alt-after" data-expectedlabel="start alt-before end label start alt-after end" data-testname="button name from fallback content mixing attr() and s