ladybird/Tests/LibWeb/Text/input/DOM/CharacterData-substringData-break-surrogate-pair.html

<script src="../include.js"></script>
<script>
    test(() => {
        const str = '\uD83D\uDC36'; // 🐶
        let t = document.createTextNode(str);
        println("Before substringData:");
        for (let i = 0; i < t.length; ++i) {
            println("[" + i + "]: " + t.data.charCodeAt(i));
        }

        // Break the surrogate pair
        const invalidSubstring = t.substringData(0, 1);
        println("After substringData(0, 1):");
        for (let i = 0; i < invalidSubstring.length; ++i) {
            println("[" + i + "]: " + invalidSubstring.charCodeAt(i));
        }
    });
</script>