chromium/third_party/blink/web_tests/fast/multicol/flipped-blocks-hit-test.html

<div style="
    width: 100px;
    height: 200px;
    -webkit-columns: 2;
    -webkit-column-gap: 0;
    columns: 2;
    column-gap: 0;
    column-fill: auto;
    writing-mode: vertical-rl;
    font: 20px Ahem;
">
    1111 2222 3333 4444 5
    <div></div>
</div>
<p id="result">The test did not run.</p>
<script>
    if (window.testRunner)
        testRunner.dumpAsText();

    var offset = document.caretRangeFromPoint(18, 38).startOffset;
    document.getElementById("result").innerText = offset === 26 ? "PASS" : "FAIL";
</script>