Inserting document into Mongodb with NodeJs returns document but it is not in collection

I have a weird issue where I have a test to see prove that you cannot create a new user if a user with the same name/email exists, however it always seems to fail. However when I look at the first step which adds a user to the database with the details expected, it inserts and calls back with the document:

[ { Username: 'AccountUser',
    Email: 'some@email.com',
    CreatedDate: Mon Sep 22 2014 12:52:48 GMT+0100 (GMT Summer Time),
    _id: 54200d90d0a34ffc1565df13 } ]

So if I do a console.log of the documents returned from insert thats what I get which is ok, and the _id has been set by mongo which is correct, so I know the call succeeded, and there was no errors.

However if I then go and view the database (MongoVUE) that collection is empty, so I am a bit baffled as to why this is happening.

I am using pooled mongodb connections (i.e setting up during app setup then using app.set("database_connection", database);. So I am a bit baffled as to why this is happening?

Here is some example code, which is part of larger code but basically is contained within promises:

// Point of connection creation
var mongoClient = mongodb.MongoClient;
var connectionCallback = function (err, database) {
    if (err) { reject(err); }
    resolve(database);
};

try
{ mongoClient.connect(connectionString, connectionCallback); }
catch(exception)
{ reject(exception); }

// Point of usage
var usersCollection = connection.collection("users");
usersCollection.insert(userDocument, function(err, docs) {
    if(err) {
        reject(err);
        return;
    }

    console.log(docs);
    resolve(docs[0]);
});

So I create the connection and pass back the database for use elsewhere, then at the point of inserting I get the connection, get the collection and then insert into it, and log the documents added, which is what is in the above log output.

Also finally running:

• Windows 8.1
• Node 0.11.13
• npm mongodb latest
• MongoDB 2.6.1