ttributes of inherited interfaces which do not declare a [Default] toJSON operation.');

    test(function() {
        var context = new IdlArray();
        context.add_idls("interface D { attribute DOMString d; };");
        context.add_idls("interface mixin M { [Default] object toJSON(); attribute long m; };");
        context.add_idls("D includes M;");
        context.merge_mixins();
        var map = context.members.D.default_to_json_operation();
        assert_array_equals([...map.keys()], ["d", "m"]);