https://github.com/mongodb/js-bson/issues/384 

As described in the issue, the inner logic for determining whether to serialize as Long/Double is never reached because of the outer condition for:

value >= constants.JS_INT_MIN &&
value <= constants.JS_INT_MAX

However, simply removing the outer condition causes these tests to fail.

It's not immediately clear how we should deserialize Longs which are larger than Number.MAX_SAFE_INTEGER.