I generally use virtual machines for testing, however, you can sometimes run into problems with this. For example: I recently discovered a javascript / flash interaction bug in IE that only exists in a VM environment. In the past, I've run into strange IE css rendering bugs in a VM as well. These are really few and far between, but they do happen, and have been documented issues with virtualized environments. If you are testing on a VM and you run into a bug that just doesn't make any sense, try running it on a real box with the exact same setup.

I was about to post the same thing. If you don't have an old PC laying around, running a VM is an easy way to test an application with limited resources. Another tip on is to setup another user account on your system with large fonts to quickly test DPI scaling.

Is there a way to emulate varying processor speeds using VirtualBox or other VMs?