It sounds like you want a way to extend the existing PlatformAttribute with your own code, so that you could write something like: [Platform("SerialPortAIsAvailable")] and place it on a test or a fixture - or even at a higher level SetUpFixture. This is a major bit of work, which is planned for NUnit 3.0. In fact, we probably will replace the PlatformAttribute with something more general like [Include] and [Exclude] allowing for automatic detection of Operating System, Runtime, Culture and a few other things by NUnit, together with a way to extend it with your own tags and code. If this is the sort of thing you are after, I'll kick this bug to NUnit 3.0. If you're looking for something simpler please clarify before I do that! As a workaround, I suggest you put an Assume(SerialPortAIsAvailable) at the head of each test requiring it. This is a bit less intrusive than the code you gave above and will give an Inconclusive result when the port is not available. It will not give you a yellow bar, but you can do that by simply including one test that uses Ignore as above. By the way, I hope you have told us about whatever problems prevent you from upgrading to 2.6.2. Obviously, any fix we make for this will be in a future release, so you'll eventually want to upgrade. IME, waiting too long makes it harder. Charlie On Fri, Dec 28, 2012 at 4:46 AM, Matthias Kläy