'undefined');
    }, nodeName + '.append() with undefined as an argument, on a parent having no child.');

    test(function() {
        const parent = node.cloneNode();
        parent.append('text');
        assert_equals(parent.childNodes[0].textContent, 'text');
    }, nodeName + '.append() with only text as an argument, on a parent having no child.');

    test(function() {
        const parent = node.cloneNode();
        const x = document.createElement('x');
        parent.append(x);
        assert_ar