When you try to run a test in MTM you get a dialog ‘Object reference not set to an instance of an object’

When trying to run a newly created manual test in MTM I got the error dialog

‘You cannot run the selected tests, Object reference not set to an instance of an object’.

On checking the windows event log I saw

Detailed Message: TF30065: An unhandled exception occurred.

Web Request Details Url: http://……/TestManagement/v1.0/TestResultsEx.asmx

So not really that much help in diagnosing the problem!

Turns out the problem was I had been editing the test case work item type. Though it had saved/imported without any errors (it is validated during these processes) something was wrong with it. I suspect to do with filtering the list of users in the ‘assigned to’ field as this is what I last remember editing, but I might be wrong, it was on a demo TFS instance I have not used for a while.

The solution was to revert the test case work item type back to a known good version and recreate the failing test(s). Its seems once a test was created from the bad template there was nothing you could do about fixing it.

Once this was done MTM ran the tests without any issues.

When I have some time I will do an XML compare of the exported good and bad work item types to see what the problem really was.