The reason why the tests were no longer passing is because I removed the replication accidentally when I removed the triple assignment. I couldn't explain why I used the "triple assignment" code `$schemas->{$name} = $schemas->{$name}->clone` previously and assumed I made a mistake but that was in-fact what was required. 

Normally, this plugin reads the configuration and caches a connection to the database (which is not slave-aware); the code I added checks for the `read_slaves` configuration and if found replaces the initial connect with one which is slave aware. It also creates a lexically scoped reference to the handle for convenience. That's what this triple assignment was doing.