I was stepping through one of my unit tests, and all of a sudden Visual Studio pops up an error:

"The Visual Studio performance and coverage logging engine is already running on the computer. Therefore, the test run cannot continue. Close the pending performance or code coverage session and then rerun the tests"

Hmm, I was not running an actual performance session at the time, but I was experimenting with that a few days ago.

So I stopped all sessions and closed all performance related tool-windows. Visual Studio still couldn't run the tests. Not even after restarting it...

Luckily, the error message is quite clear, so I found that  you should kill VSPerfMon.exe.

And we're back in business....