Objective: Investigate if unified reactive ChangeStream tests can be made to comply with unified JSON commands order, avoiding race conditions.

Background: Race conditions occur when executing an aggregate command followed immediately by getMore commands, leading to test failures in the "expected events" stage.

Partial Workaround: There is a partial workaround implemented in JAVA-5356 . This approach waits for the BatchCursor creation or catches errors if the creation fails. However, it does not address the issue: it does not suspend operations after an aggregate command until "next" or "hasNext" is called on SyncMongoCursor.

Required Investigation:

• Determine if it's feasible to enforce command order/a pause in reactive streams post-aggregate operation until a specific trigger (like "next" or "hasNext") in SyncMongoCursor.