run_single_test.el

(defun cabbage-ruby-test-run-file (filename)
  (interactive (list(buffer-file-name)))
  (let* ((name-buffer "ruby-test")
         (name-buffer-full (format "*%s*" name-buffer)))

    (display-buffer (get-buffer-create name-buffer-full))
    (with-current-buffer name-buffer-full
      (erase-buffer))
    (display-buffer name-buffer-full)
    (ruby-compilation-do name-buffer (cons "ruby" (list filename)))))