[Orgmode][babel] Problem using noweb

[andy]

I want to take advantage of babel's noweb capabilities, but I can't seem
to get it to work. I'm sure there is something trivial wrong with my
source block, but after looking at the documentation and looking at the
examples I can find on the web, I think this should work.

I define a variable in test-block, but it's not there, even though
test-block should be getting pulled in when I run the source block, bar.
What am I doing wrong? My .emacs has R defined and indeed, the session
*R* starts up without any problems and the print statement works, but
test-block just isn't there.

* Foo
** Bar
#+src_name: bar
#+begin_src R :noweb yes :session *R*
  <<test-block>>
  print("I am here")
  a
#+end_src

* test-block
#+src_name: test-block
#+begin_src R :session *R*
  a <- c(1,2,3,4,5)
#+end_src


thanks
--andy