Optimistic Concurrency MongoDB

gistfile1.cs

[Subject("Mongo")]
public class when_issuing_an_update_on_a_changed_entity : mongo_context
{
    private static long DocumentsAffected;

    private Establish context = () => SetUpDatabase();
    private Because of = () => DocumentsAffected = UpdateSameObjectTwice();
    private It should_not_affect_any_documents = () => Assert.That(DocumentsAffected, Is.EqualTo(0));

    private static long UpdateSameObjectTwice()
    {
        var events = db.GetCollection("events");
        var oldRevision = events.AsQueryable().First().Revision;

        SomeoneChangedDocument();

        var res = events.Update(
            WhereDocHasRevision(oldRevision),
            Update.Set("Revision", new BsonInt32(100)),
            SafeMode.True);
        return res.DocumentsAffected;
    }

    private static void SomeoneChangedDocument()
    {
        var events = db.GetCollection("events");
        var evt = events.AsQueryable().First();
        evt.Revision++;
        events.Save(evt);
    }

    private static IMongoQuery WhereDocHasRevision(int oldRevision)
    {
        return Query.And(
            Query.EQ("_id", "1"),
            Query.EQ("Revision", new BsonInt32(oldRevision))
            );
    }
}