[Pythonmac-SIG] Testing applications with console input?

[Kevin Horton]

On 21 May 2007, at 19:27, Gary Bernhardt wrote:

> On 5/21/07, Kevin Horton <khorton01 at rogers.com> wrote:
>> I'm working on a small application that will respond to user input
>> via the console.  It is a very simple interface, with user input via
>> "raw_input()", and the application produces result via "print"
>> statements.  I'm using python 2.5.1 on OS X, installed via Fink, but
>> I'll also use the application with Movable Python 2.4.3 on Windows.
>>
>> I've got unit tests for many of the discrete units, but I still need
>> to write some tests for the user interface, to help catch problems
>> when refactoring code, etc.  I've searched the web, but I can't find
>> any description of how to write tests for such a user interface.  Any
>> advice would be appreciated.
>
> Two methods come to mind:
>
> 1. popen your program from the test and interact with it that way.
> This is pretty easy with the subprocess module.

subprocess looks interesting.  I played a bit in iPython, and managed  
to get a response from my program, so this might work.

> 2. Modify your program to use a slightly more abstract IO interface.
> This can be as simple as a class that has input() and output()
> functions.  Under normal conditions, it just passes the calls on to
> 'raw_input' and 'print'.  To test it, you can monkey patch the program
> to use an alternative IO class that puts the test in control.  Or if
> you're feeling fancy, you can use dependency injection to achieve the
> same effect.

I'm a python newbie, so this approach looks a bit daunting at the  
moment.  But, it might be a good way to learn a lot of useful stuff.

> These are just off the top of my head, so there may be pitfalls. :)
> I'd probably favor #2 because spawning processes can bloat your tests
> up and slow them down.  Then again, it sounds like you're looking for
> a system test, not a unit test, so maybe spawning a process is the
> right thing to do.

Yes, I really am doing full system tests, so I want to simulate "real  
world" user interaction with my program as closely as possible.   
Speed is not a huge issue, within reason.

> By the way, there's a pretty new testing-in-python list that's quite
> good for this kind of question:
> http://lists.idyll.org/listinfo/testing-in-python

I had seen mention of this on someone's python blog, but had  
forgotten about it.  Thanks for the reminder.  I'll have a look at  
the list archives, and probably dare a newbie question.

Thanks,

Kevin Horton
Ottawa, Canada