I've created a new user on a clean database, but can't connect with it. I can, however, connect with no credentials.
PS C:\Program Files\MongoDB\Server\3.0\bin> .\mongo.exe localhost/test
MongoDB shell version: 3.0.11
connecting to: localhost/test
> var me = { user: 'dave', pwd: 'password', roles: [ 'userAdminAnyDatabase'] }
> use admin
switched to db admin
> db.createUser(me)
Successfully added user: { "user" : "dave", "roles" : [ "userAdminAnyDatabase" ] }
> ^C
bye
PS C:\Program Files\MongoDB\Server\3.0\bin> .\mongo.exe -u dave -p password
MongoDB shell version: 3.0.11
connecting to: test
2016-04-27T15:40:38.185+0100 E QUERY Error: 18 Authentication failed.
at DB._authOrThrow (src/mongo/shell/db.js:1271:32)
at (auth):6:8
at (auth):7:2 at src/mongo/shell/db.js:1271
exception: login failed