m"));
        fd.append('key', null);
        fd.append('key', 'value1');
        assert_equals(fd.get('key'), "null");
    }, 'testFormDataAppendToFormNull2');
    test(function() {
        var fd = new FormData(document.getElementById("form"));
        assert_throws_js(TypeError, () => {fd.append('name', "string", 'filename')});
    }, 'testFormDataAppendToFormString');
    test(function() {
        var fd = new FormData(document.getElementById("form"));
        assert_throws_js(TypeError, () => {fd.appen