While developping an application, it is a good practice to test on the targeted platforms to ensure that everyhing goes well. If you are developing on Mac OS X 10.6, it can be challenging to know if the application will still run on Mac OS X 10.5. You have two solutions:

- Get two other Mac hardware and set them up with Mac OS X 10.5 and Mac OS X 10.6. When tests are needed, transfer your application to the testing hardware. - Virtualize Mac OS X 10.5 and Mac OS X 10.6 on the development machine, and fire the virtual machine when tests are needed. This second option is the best option, as all you need is a lot of disk and RAM.

In order to virtualize Mac OS X 10.5/10.6, you are bound to the following restrictions:

- Virtualization takes place in VMWare Fusion. You must run it on genuine Mac hardware. - Only Mac OS X Server can be virtualized as per the Apple EULA. It is not a problem as the only difference between a desktop and a server version is software only. A good way to get Mac OS X Server images is to enroll in the Mac Developer Program.

VMWare Fusion makes a breeze to create, run and operate Mac OS X Server virtual machines. So, you can now test on Mac OS X 10.5 and 10.6 on your development machine.