Testing database application is hard enough when you have only one server. When you need to test performance and scalability by involving multiple servers, then you need either a lot of patience or a tool that can simplify your task.
Using MySQL Sandbox, you can install single or multiple nodes in one host. Combining that with Gearman, a client/server infrastructure for generic tasks, you can work on distributed servers easily, with little worry about the details.
No matter what language you speak, Gearman can meet your needs in C, PHP, Perl, Ruby, shell scripting, and several more.

There are many GUI applications to deal with databases and with MySQL in particular. But for die hard command line enthusiasts, who grew up with Linux, the shell prompt is still prince.
You would be surprised at the vast amount of operations that you can do from the command line. Running commands on several databases at once, filtering users, getting detailed metadata, transferring data from the operating system to a database and the other way around, creating scripts from database data, creating SQL commands from database data.