When I write several source blocks, which depend on one another, I tend to debug them one by one.

So, I write this function and test it:

#+NAME: square

#+BEGIN_SRC python

    square = lambda x: x * x

    return square(5)

#+END_SRC

#+RESULTS: square

: 25

After I see that the test is successful, I write this client function:

#+BEGIN_SRC python :noweb yes

    <<square>>

    return 5 + square(5)

#+END_SRC

#+RESULTS:

: 25

And here, to get the correct result, I have to remove the ~return square(5)~ line in ~<<square>>~.

But I don't want to lose testing!

So I find nothing better to do than to seperate the source block:

#+NAME: square-1

#+BEGIN_SRC python

    square = lambda x: x * x

#+END_SRC

And, by the way, there was no error/warning that I have just redefined ~<<square>>~,

so, for the test-snippet below to work, I renamed it to ~<<square-1>>~.

I think the org-mode team is aware of it, but anyway:

- [ ] no error checking of the description of a code block.

#+NAME: square-1-tester

#+BEGIN_SRC python :noweb yes

  <<square-1>>

  return square(5)

#+END_SRC

#+RESULTS: square-1-tester

: 25

- [ ] For every such source block used for testing purposes, you have to repeat the inclusion statement and part of the name, which is cumbersome.

A fair solution is maybe to extend the block like this:

#+NAME: square-1

#+BEGIN_SRC python

  square = lambda x: x * x

#+END_SRC

  return square(5)

#+END_SRC_TEST

When I call this individually, the test part would run, but when I :noweb it in another block, the test part would be ommited.

As an extension of this idea, it could be useful to have several test attachments like this, each producing its own result. Maybe, the TEST part could as well be ommited. Custom names are also an option:

#+NAME: square-multiple

#+BEGIN_SRC python

  square = lambda x: x * x

#+END_SRC

  return square(5)

#+END_SRC NAME: ext_1 

  return square(10)

#+END_SRC NAME: ext_2 

#+RESULTS: square-multiple-ext-1

: 25

#+RESULTS: square-multiple-ext-2

: 100

Overall, these techniques should reduce noise and increase usability.