SERVER-99139 introduced a smoke test covering basic functionality of the addShard and removeShard commands; test cases aren't nevertheless run in full isolation from each other, since the commands are currently targeting the shards provisioned by the backing ShardingTestFixture, which have to be reused across test cases. This situation is also preventing key test cases from being properly expressed.

The objective of this ticket is to explore the feasibility of instantiating extra replica sets (for example, through ReplSetTest) as a way of bridging such a gap.