Does IETester run the ACTUAL same code that existed for IE6 / IE7? Or is it an emulation?

Question

I just realized (yes, this was stupid of me) that IE8 Compatibility Mode is NOT IE7.
All the time I assumed they would be switching back to the IE7 binaries, which apparently they aren't, as indicated by another question I found here in SO.

My question is...
Does anyone know how IETester works?
Does it run the actual binaries for IE6/7?
Can I trust it for my tests as being IE6/7?
Or should I consider it a "close" thing, but actually test in actual VMs to be 100% sure?

Thanks!

Answer 1

Experience had taught me that MultiIE/IETester et al, are never 100% accurate, when you're running other versions of IE.

I would run the VM versions to be 100% sure.

Answer 2

Yes, the only true test is to use the vhd's. ietester is slow and bugridden & has issues with iframes & script sometimes + you dont get the cover across all the OS ie versions either which can make a big difference.