如何在使用sinon时模拟mongo更新错误

Question

参考：Integration testing with mongojs to cover database errors

链接的场景与使用mongoskin的我的集成测试相同，以覆盖db错误。

var mongoskin = require('mongoskin');
var db = require('./setting').DB;
var collection = db.collection('test');
var route = require('express').Router();

...
route.post('test', function(req,res) {
    db.collection('test').update({...}, {...}, function (err, data) {
        if (err) {
            // this code should be tested
            logger.error(err);
            return;
        }

        // all is good, this is usually covered
    });
});

file.test.js

var sinon = require('sinon');
var rewire = require('rewire');
var tc = rewire('./file');
var superagent = require('superagent');
var mongoskin = require('mongoskin');
var db = tc.__get__('db');

it('xx', function(done){
    var update = sinon.stub().yields(new Error('error'));
    sinon.stub(db, 'collection').returns({update: update})

    superagent.post(url).send(data).end(function(e,res){
        done();
    });
})

我尝试但无效。

帮助。我希望模拟更新mongodb并将错误设置为第3个arg，logger输出尖叫。