Add tests to cover conditions (need to prio and decide which are important/covered):

• No dbs
• Empty db(s)
• No indexes on a collection
• Lots of indexes on a collection (more than limit)
• Losing sync source (due connection timeout versus query/command timeouts)
• Changing to a new sync source after a failure in a previous attempt
• Active writes during clones (start OpTime != end OpTime)
  • With new databases/collections create
  • With new unique indexes (and updates which violate unique index constraint during apply phase)
  • With map/reduce, apply ops, drop/create, etc.
• Sync source rollback during
  • Collection clone
  • While getting latest oplog OpTime (for minvalid)
  • Oplog apply phase