My unit tests were running fine and then for some reason the results started coming back as "Not Executed".
Trying to open the test to get more information only reports "The test has not been executed".
The problem persisted after a restart.
Clicking on the "Test run error" message in the yellow error reveals the issue.
Failed to queue test run 'dballinger@XXXXX 2010-01-25 13:51:40': Test Run deployment issue: The location of the file or directory 'd:\development\projectX\projectX.namespace\bin\debug\Ionic.Zip.dll' is not trusted.
Turns out a new third party DLL that I had added was marked as blocked when it came out of the zip file. More details here Stack Overflow: Why are all my Visual Studio test results “Not executed”