Brad Johnson of Borland has a new article on the issues of testing in a virtualized environment at http://java.sys-con.com/read/430982.htm.

Recently PushToTest partnered with ReplicateTech to offer our customers a virtual test bed environment. So reading Brad's article brought-up several issues.

Here is what Ken Novak of ReplicateTech told me about Brad's article:

Brad Johnson does a good job of describing the value of virtualization. Saving 
and restoring the coordinated state of multiple machines can accelerate the whole
testing process. 

Keeping the machines in a coordinated state can get complicated.  Many files are
involved, of course, totaling many gigabytes.  Other attributes of the vms - how they
are "wired" together, which ports are used for VNC or SSH access, how files are moved
between machines, what usernames and passwords are used - must be nailed down and kept
consistent through changes, much like a physical testbed.  As a result, virtual
testbeds that are shared between users need either custom scripts or a software 
package to keep things straight. 
The article mentions one case involving "a custom application running in a data 
center in a foreign country".  Complex networks can be part of a virtual testbed,
though it creates special challenges.  At Replicate, we augment a virtual lab with
virtual machines that serve as routers, VPN terminators, and network latency and loss
simulators, to produce realistic network conditions. 

-Frank