Tuesday, December 22, 2009

Visual Studio Unit Tests fails to run

After debugging some unit tests, I couldn't rerun my tests. I get a big warning icon and a very useful message telling me that the tests were not executed. After scrolling through the endless list of test run details I found following error message at the bottom;

“Code coverage collection 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.”

The solution is to shutdown the VSPerfMon.Exe process which gets left in memory when you debug a unit test and stop the debugger before the test finishes.

More information can be found here at Microsoft Connect