Currently when symbols and integers are converted between bson, ruby types and extended json the type information is not preserved, and hence these types cannot always be round-tripped. This ticket covers adding support for round-tripping symbols and integers:

Add BSON::Symbol::Raw type that encodes to BSON symbol, permitting Symbol round-tripping
Add mode: :bson to .from_bson methods everywhere which will yield BSON::Int64 instances, permitting int64 round-tripping
Add bson corpus spec tests dealing with int64 and symbol