VS 2010 Test Runner error “The agent process was s

Question

In Visual Studio 2010, I have a number of unit tests. When I run multiple tests at one time using test lists, I sometimes reveive the following error for one or more of the tests:

The agent process was stopped while the test was running.

It is never the same test failing, and if I try to run the test again, it succeeds.

I found this bug report on Connect, which seems to be the same problem, but it does not offer a solution.

Has anyone else seen this behaviour ? How I can avoid it ?

Edit

I am still experiencing this bug, and so is many of my colleagues on the same software/hardware setup. I have evaluated the answers so far, but they don't resolve the problem. I am starting a bounty for a solution to this problem.

Answer 1

I had the same problem and it was caused by a finalizer for an unmanaged resource (a file writer that was not getting disposed properly for some reason).

After wrapping the finalizer code in a try-catch that swallows the exception, the problem disappeared. I don't recommend swallowing exceptions like that, so it would obviously be wise to find out why the exception is occurring in the first place.

Answer 2

I was having this problem, and it turned out to be a problem in my code which the Test Framework wasn't catching properly. A little accidental refactoring had left me with this code:

public void GetThingy()
{
    this.GetThingy();
}

This is of course an infinite recursion, and caused a StackOverflowException (I guess). What this caused was the dreaded: "The agent process was stopped while the test was running."

A quick code inspection showed me the problem, and my tests are now running fine. Hope this helps - might be worth inspecting the code looking for issues, or maybe extracting a bit into a console app and checking it works properly there.

Answer 3

I was able to find the source of my problem by looking in the test result file (/TestResults/*.trx) It provided the full details of the exception that occurred in the background thread, and once I resolved that exception the "agent processed stopped..." error went away.

In my case I was unintentionally launching the GUI in my unit test, which eventually caused a System.ComponentModel.InvalidAsynchronousStateException to be thrown.

So my .trx file contained:

   <RunInfo computerName="DT-1202" outcome="Error" timestamp="2013-07-29T13:52:11.2647907-04:00">
    <Text>One of the background threads threw exception: 
System.ComponentModel.InvalidAsynchronousStateException: An error occurred invoking the method.  The destination thread no longer exists.
at System.Windows.Forms.Control.WaitForWaitHandle(WaitHandle waitHandle)
at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
at System.Windows.Forms.Control.Invoke(Delegate method)
...
</Text>
  </RunInfo>

This didn't provide any information on what test caused the error, but it did show me where the exception was, which was very useful.

Answer 4

In my case the solution was resolved by checking the Output Window.

'QTAgent32.exe' (Managed (v4.0.30319)): Loaded 'C:\TestResults\bdewey_XXXXXX072 2011-01-11 17_00_40\Out\MyCode.dll', Symbols loaded. E, 9024, 9, 2011/01/11, 17:00:46.827, XXXXX072\QTAgent32.exe, Unhandled Exception Caught, reporting through Watson: [Exception message]

In my case I had a FileSystemWatcher that was throwing an error on a seperate thread.

Answer 5

I've just experienced the similar problem: some tests fail and they are different in different test runs. I don't know exactly the reason why it happens, but it began to occur when I added a finalizer to one of my classes. When I disable the finalizer - the problem disappears. When I turn the finalizer on - the problem comes back.

Right now I don't know how to overcome this.

Answer 6

This message is typically generated when the test process crashes and can happen when there is an unhandled exception on a background thread, a stack overflow occurs, or an explicit call to Process.GetCurrentProcess().Kill() or Environment.Exit. Another possible cause is an access violation in unmanaged code.

Something no one has mentioned is that there may be additional information in the event log. Usually you will not get much information on why the test crashed in the results, however in the event of an unhandled exception on a background thread, then the test framework writes details to the Application event log with source VSTTExecution. If there is no information written to the event log then it is likely one of the other causes listed above.