From: Philip Murray <pmurray@...>
Date: 2007-08-08T13:06:59+09:00
Subject: Re: capturing stdout during unit tests

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On 8/08/2007, at 3:59 PM, Mark Slater wrote:

> I've written a script for use with Nagios (a monitoring tool) that  
> I'd like to test. The requirements for the script is that it output  
> a single line of text to STDOUT and then exit with a status code (0  
> - 3). My script is designed to monitor a few different services...  
> each invocation includes a required command line argument  
> specifying the service to monitor in the current invocation. To do  
> that, I created a class for each type of service monitor.
>
> I'm now writing unit tests for my script, and I'd like to check  
> that the output written to STDOUT by each service monitor class is  
> correct. But I'm new to Ruby and I'm not sure how to do that. In  
> other languages, I'd simply redefine STDOUT as a stream that goes  
> to a large in-memory buffer, but I haven't seen anything that  
> suggests that is possible in Ruby. The best I've come up with so  
> far is creating a temporary file and calling $stdout.reopen() with  
> the path to that temporary file. However, I'd much rather do this  
> in memory because then I never have to worry about what file system  
> and permissions the user executing the unit test has.
>
> Thanks,
>

Try this:

require 'stringio'

$stdout = StringIO.new

(This will break in IRB w/ Readline)

StringIO has all the IO methods, but acts on a string, not a file. So  
you should be able to do what you want.

Cheers

Phil
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