From: Mark Slater <lists@...>
Date: 2007-08-08T12:59:49+09:00
Subject: capturing stdout during unit tests

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,

Mark