).default_to_json_operation();
        assert_equals(map.size, 0);
    }, 'should return an empty map when there are no attributes');

    test(function() {
        var r = interfaceFrom('interface A { };').default_to_json_operation();
        assert_equals(r, null);
    }, 'should return null when there is no toJSON method');

    test(function() {
        var r = interfaceFrom('interface A { DOMString toJSON(); };').default_to_json_operation();
        assert_equals(r, null);
    }, 'should return null wh