chromium/third_party/blink/web_tests/fast/css-generated-content/attr-missing.html

<style>
    span::before { content: attr(foo); }
</style>
<span></span>
<script>
    if (window.testRunner)
        testRunner.dumpAsText();
</script>
<p>
    Test for <i><a href="https://bugs.webkit.org/show_bug.cgi?id=71085">https://bugs.webkit.org/show_bug.cgi?id=71085</a>
    Assertion failure (m_text) in LayoutText::LayoutText() at icanhascheezburger.com</i>.
</p>
<p>
    The test passes if it does not cause an assertion failure in a debug build.
</p>