The .NET blog

In case you haven’t noticed, testing your applications on several machines is a very good idea, especially in that pre-beta phase, where you want to get rid of the most obvious bugs before showing your work for the first time. Especially with the .NET framework, testing your work on other machines than the one it’s being developed on is recommendable. You could easily have forgotten to include a specific assembly, or include an older version than the one you are currently using. Another common pitfall is to develop on Windows XP, and not testing on Windows Vista. A lot of things have changed, and some of them may break your application. And it goes the other way too - in my experience, several things which will work just fine on XP, will not work as well on a Windows 2000 machine.

Now, don’t go out and buy 2-3 new computers, with different OS’ on them. This scenario is perfect for the Virtual Machine. Many people swear by vmware, which is supposed to be really good, but personally I just use Microsoft Virtual PC 2007. With version 2007, it can now be downloaded and used for free, and in my experience, it’s very stable and extremely easy to use.

The absolute top feature of a virtual machine for software developers, is the undo disk feature. It allows you to boot the VPC, work on it, and then delete all changes. This gives you the possibility to test your application on a clean machine each time. Once you have installed a version of Windows in your Virtual PC, select it from the list and click Settings. Now, from the list of options, select Undo Disks and make sure that it has been enabled. Now, boot the OS, make it comfortable for you to work with (for instance, I always enable the display of file extensions, because I hate not being able to see them) and visit Windows Update and make sure that it’s fully updated. Once you close the system, make sure that you commit the changes to disk. You now have a fully functional test OS, and whenever you use it for testing purposes, just make sure that the “Commit changes to disk” is not checked, and the changes you have made will not be persisted. You may still choose to save changes from session to session, but it will be stored separately, and only committed to your VPC if you want it to - if not, simply select the delete option upon closing the OS.

With a setup like this, you have clean and mean testing environment for your applications