Running Rdevtool::test_that on buffer save in ESS

My workflow:

• Hack away at an .R or test_*.R file
• Save buffer.
• Switch to window with *R* process
• hit C-p, RET. to re-evaluate devtools::test()

To me, this seems far too arduous. Why can't I get R to run devtools::test() automatically when I save the buffer? Please help, my fingers can barely take the strain of the seven extra keystrokes!

This worked for a similar setup (switching to a shell buffer):

(defun devtools-test ()
  (interactive)
  (when (string-match (rx-to-string `(: ".R" eos) t) (buffer-name))
    (switch-to-buffer "*R*")
    (end-of-buffer)
    (insert "devtools::test()")
    (comint-send-input)))

(add-hook 'after-save-hook 'devtools-test)

Does that work for you?