[Edu-sig] testing interactive loops

[Andre Roberge]

On 5/16/06, Andrew Harrington <aharrin at luc.edu> wrote:
>
> We have been discussing testing in tutorials with doctest.
> There is one place that does not work, I think:  testing an interactive
> loop, which is a construction I teach in introductory programming.
>
> It appears that doctest cannot handle interactive input.  I would still
> like to be able to illustrate a session with interactive input and
> explicit output at the end, and check it automatically.
>
> If you just do input redirection and compare the actual output to the
> desired input, you get messed up because the input is not echoed when
> you redirect from a file.
>
> The following does not work, but is the idea you want, to force the echo
> when stdin become a file:
>
> orig_raw_input = raw_input
>
> def raw_input_echo(prompt=""):
>     s = orig_raw_input(prompt)
>     print s
>     return s
>
> raw_input = raw_input_echo
>
> def input_echo(prompt=""):
>     return eval(raw_input(prompt))
>
> This fails because it makes raw_input a global for the current module,
> but not a built_in, so it fails when you import and use a module using
> raw_input.


How about:  (something totally untested)
import ah  # module named after you :-)
ah.raw_input = raw_input_echo

And then you run your tests?...

André

I guess we could make it work in little code fragment tests, where you
> append the user's fragment to the code above, in the same module, but it
> is not a general solution.
>
> Is there any better way to do this?
>
> A kludge for tutorial doc tests would be to mark the prompt strings
> somehow in the tutorial source, for instance making it always end with
> :: or ?? so the test string can be parsed to find the responses that
> come after the prompts, and put them in the input file and not in the
> output file.  For example, the test string
> ... Sum numbers!
> ... Enter a number (or 0 to quit):: 3
> ... Enter a number (or 0 to quit):: 4
> ... Enter a number (or 0 to quit):: 8
> ... Enter a number (or 0 to quit):: 0
> ... The sum is 15!
>
> might be processed for web display in the tutorial undoubling the ::
>
> ... Sum numbers!
> ... Enter a number (or 0 to quit): 3
> ... Enter a number (or 0 to quit): 4
> ... Enter a number (or 0 to quit): 8
> ... Enter a number (or 0 to quit): 0
> ... The sum is 15!
>
> and the tutorial parser would also generate an input file
> 3
> 4
> 8
> 0
>
> and output file
>
> Sum numbers!
> Enter a number (or 0 to quit):
> Enter a number (or 0 to quit):
> Enter a number (or 0 to quit):
> Enter a number (or 0 to quit):
> The sum is 15!
>
> Then run the code with redirection and compare the desired and actual
> output.  There still is the issue of the program hanging with the given
> input ...
>
> How does regular doctest deal with infinite loops or waiting for
> nonexistent keyboard input?


??


Better ideas?
>
> --
>   Andrew N. Harrington
>   Computer Science Department      Undergraduate Program Director
>   Loyola University Chicago        http://www.cs.luc.edu/~anh
>   512B Lewis Towers (office)       Office Phone: 312-915-7982
>   Snail mail to Lewis Towers 416   Dept. Fax:    312-915-7998
>   820 North Michigan Avenue        aharrin at luc.edu
>   Chicago, Illinois 60611
>
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