container.setHTMLUnsafe(`<div id="textDiv" class="user-select-none">aaa</div>`);
    const textDiv = document.getElementById("textDiv");
    const rect = textDiv.getBoundingClientRect();
    const characterWidth = rect.width / textDiv.textContent.length;
    const characterIndex = 2
    const x = rect.left + characterWidth * characterIndex;
    const y = rect.top + rect.height / 2;
    const caretPosition = document.caretPositionFromPoint(x, y);
    assert_true(caretPosition instanceof CaretPosition);
    a