I just updated emacs-rails so that feedback on the currently running test is put in the global modeline. This means you get that feedback in all buffers, so you can work on something else while your tests are running, and the minibuffer stays free for useful things.
It’s started automatically when emacs-rails is loaded, but that’s customizable of course, and you can switch it on and off using rails-ui:enable-mode-line / rails-ui:disable-mode-line.
Update: actually, the head has some nicely cleaned up code now. So just get that at http://github.com/remvee/emacs-rails/tree/master