 assert_equals(map.get("bar").idlType, "DOMString");
    }, 'should return a map whose key/value pair represent the identifier and IDL type of valid attributes');

    test(function() {
        var context = new IdlArray();
        context.add_idls("interface A : B { [Default] object toJSON(); attribute DOMString a; };");
        context.add_idls("interface B { [Default] object toJSON(); attribute long b; };");
        var map = context.members.A.default_to_json_operation();
        assert_array_equals([...