chromium/third_party/blink/web_tests/fast/forms/caret-rtl.html

<!doctype html>
<script src="../../resources/ahem.js"></script>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<div CONTENTEDITABLE id="test" style="direction: rtl; width:200px; font-family: Ahem; font-size:2000%; outline: solid thin"></div> 
<script>
// Click in the div, the caret should be on the right edge of the div.
test(() => {
    const selection = window.getSelection();
    const target = document.getElementById('test');
    target.focus();
    selection.collapse(target, 0);
    if (!window.internals)
        throw 'This test requires internals.';
    const rect = internals.absoluteCaretBounds();
    assert_equals(`(${rect.left},${rect.top})+${rect.width}x${rect.height}`,
                  '(207,8)+1x320');
}, 'This tests that clicking in a contenteditable div will set the caret in the right edge of the div');
</script>