If you only want to test the behavior of the server you can just hand in two channels and fake messages on those in your server tests (i.e. no IRC Bridge is created at all). I think this is the most reasonable approach to take since you cannot rely on IRC being up when you want to test your scripts.
You can also choose not to test your new implementations, but you must at least change the setup procedure so that not necessarily an IRC connection is made when a server is created.
I do not fully understand your question.
If you only want to test the behavior of the server you can just hand in two channels and fake messages on those in your server tests (i.e. no IRC Bridge is created at all). I think this is the most reasonable approach to take since you cannot rely on IRC being up when you want to test your scripts.
You can also choose not to test your new implementations, but you must at least change the setup procedure so that not necessarily an IRC connection is made when a server is created.