lt.length, 2);
    let iter_value = result[1];
    assert_equals(iter_value.length, 1);
    assert_true(iter_value[0] instanceof type);
    assert_equals(iter_value[0].toString(), value);
}

// Run the same test twice: once for each StylePropertyMap.
//
// https://drafts.css-houdini.org/css-typed-om-1/#stylepropertymap
function test_specified_maps(func, description) {
    test(function(){
        func(target.attributeStyleMap)
    }, description + ' [attributeStyleMap]');

    test(function(){
        let r