I started using the bundled Visual Studio 2008 test tool to gradually replace NUnit tests (the main reason is to reduce the number of dependencies on my co-worker’s machines).  Generally this has been very smooth (there aren’t many differences from one system to the other really) except for one snag I ran into.  In retrospect it was a simple case of needing to read the documentation but I figured I should make a note to myself anyway especially since Google was no help in this case.

When you run unit tests using the built-in Visual Studio 2008 test tool you may notice that it will not copy the files that you have marked as "Copy To Output Directory" to the test run directory.  This is because it is actually controlled within the test settings, which is kind of a nice thing, because you can alternate between different configuration.  To tweak it go under Test -> Edit Test Run Configuration -> Local Test Run and go to the Deployment section.

One other thing to note (different from the way TestDriven runs things) is that tests are run from a TestResults directory instead of the bin\Debug directory.  This is to allow you to keep the history of test run (up to 25, by default).