text.add_idls("interface A { [Default] object toJSON(); attribute DOMString a; };");
        context.add_idls("interface B : A { attribute any b; };");
        context.add_idls("interface C : B { [Default] object toJSON(); attribute long c; };");
        var map = context.members.C.default_to_json_operation();
        assert_array_equals([...map.keys()], ["a", "c"]);
        assert_array_equals([...map.values()].map(v => v.idlType), ["DOMString", "long"]);
    }, 'should return an ordered map that ignores a