> db.createCollection("user" , {
...     validator : {
...          hoge : { $type : "array" }}})
{ "ok" : 1 }

> db.user.insert({"hoge":1})
WriteResult({
        "nInserted" : 0,
        "writeError" : {
                "code" : 121,
                "errmsg" : "Document failed validation"
        }
})

# => This is correct

> db.user.insert({"hoge":[1,2,3]})
WriteResult({
        "nInserted" : 0,
        "writeError" : {
                "code" : 121,
                "errmsg" : "Document failed validation"
        }
})

# => This is wrong!