Add a mock model for mongodb test
The origin code is from gopkg.in/mgo.v2
get this package and replace the gopkg.in/mgo.v2
mgo.Mock = true // open mock model
mgo.SetMckC("Query-All",0) // in the next function ,the first query.All() will throw an error out
// TODO:add the function need to be tested here
mgo.ClearMock() // close mock query which is seted in mgo.SetMckC()