I’ve been working in the VS10 beta trying to get my unit tests converted from nunit to mstest. Overall that went very smooth and easy thanks to some great foresight on the part of the Magenic guys who put together most of the tests.

But I keep running into issues where random tests fail due to a file IO exception:

“a procedure imported by System.Transactions could not be loaded”

The same tests may fail or work seemingly at random. After chasing this far too long, I think I’m going to assume it is a .NET 4 beta bug and just live with it for now. I can’t see where it is my code, since this code is unchanged from .NET 3.5 to 4.0, and any given test will pass around 90% of the time and fail around 10% of the time – and they only fail when run in groups of tests – so I strongly suspect something is messed up in the .NET type loader or something along that line…

Frustrating though – hopefully the next release of VS10 will magically resolve the issue.