Interesting! I was aware of Virtual Machines (multiple OS on a single server), but had never heard of Virtualized Applications. I found this page which taught me a bit more about them. Even more information can be found here.
As Linda said, Functional testing would remain the same. However, with regards to Automated testing, you must determine what KIND of testing you wish to perform.
If you are performing Automated Functional Testing, as with manual testing there would be (little or) no difference. However, if you want to perform "Back-end" or Performance testing, your approach would most likely change.
Any major automation tool will provide the capabilities you need.
However, before this topic goes any further, I suggest you clarify your question.
To clarify my question. Yes functional testing is what I was talking about.
However, I have heard from one of my colleagues who took an initial look that for example WinRunner is somewhat confused by Virtual Applications as objects don't appear to it in the same way as they normally would.
Have you heard anything similar? Have you heard of anyone who has written functional tests for Virtualised Applications?
If you are doing manual testing functional testing will not change.
However as you have discovered if you are using a tool there may be technology challenges.
For a toll you would have to verify if different virtual instances of the application present them selves in an identical way for a tool to use you would have to set up your tool scripts against the virtual application with all of its traits. If the virtual application does not look the same to the tool in all instances that you check they you may have a bigger problem which could require a lot more creativity and work or may even move you back into manual testing.
I have not failed. I've just found 10,000 ways that won't work" --Thomas Edison
"virtual application does not look the same to the tool in all instances that you check they you may have a bigger problem which could require a lot more creativity and work or may even move you back into manual testing"
... I hope to get a few virtualised applications soon so I can do some more testing. So far I've not heard of anyone who has written functionality scripts for Virtual Apps have you?