var user1 = {user: "user1", pwd: "user1", roles: ["read"]};
db.getSiblingDB("test").addUser(user1);
db.getUsers();
db.getSiblingDB("test").auth("user1","user1")
use admin
db.getSiblingDB("test").changeUserPassword("user1","xyz")
db.getSiblingDB("test").getUsers()
db.getSiblingDB("test").auth("user1","xyz")
This can cause weird behaviors if "db" isn't set or is set to a database different than the handle being used to run the helpers.