At the moment all integration tests for cold standby are using the same scenario in their tests: some content is created on the server (including binaries), a standby sync cycle is started and then the content is checked on the client. The only twist here is using/not using a data store for storing binaries.
Although good, this model could be extended to cover many more cases. For example, StandbyDiff covers the following 6 cases node/property added/changed/deleted. From these, with the scenario described, the removal part is never tested (and the change part is covered in only one test).
It would be nice to have an IT which would add content on the server, do a sync, remove some of the content, do a sync and then call OnRC. This way all cases will be covered, including if cleanup works as expected on the client.