async.js forEach vs forEachSeries

gistfile1.js

exports['forEachSeries'] = function(test){
    var args = [];
    async.forEachSeries([1,3,2], function(x, callback){
        setTimeout(function(){
            args.push(x);
            callback();
        }, x*25);
    }, function(err){
        test.same(args, [1,3,2]);
        test.done();
    });
};

exports['forEachSeries empty array'] = function(test){
    test.expect(1);
    async.forEachSeries([], function(x, callback){
        test.ok(false, 'iterator should not be called');
        callback();
    }, function(err){
        test.ok(true, 'should call callback');
    });
    setTimeout(test.done, 25);
};

exports['forEachSeries error'] = function(test){
    test.expect(2);
    var call_order = [];
    async.forEachSeries([1,2,3], function(x, callback){
        call_order.push(x);
        callback('error');
    }, function(err){
        test.same(call_order, [1]);
        test.equals(err, 'error');
    });
    setTimeout(test.done, 50);
};