Implement automated tests of concurrent db replication and modification

[richard]

Currently, there is no automated test of the behaviour when the replication function is doing a full copy of a database which gets modified while the copy is in progress.

I've done a manual test of this, so I'm moderately confident it works right, but I can't work out how to do a reliable automated test of it... at least, not without hacking a big sleep (or even a condition) into the database copying code, to allow me to be sure of getting some modifications done in the middle of it.

Any suggestions appreciated.