Lighthouse (Silverlight Unit Test Runner) hangs then performs no tests -- why?

Question

We are using Lighthouse to run unit tests on Silverlight 4 .xap files.

Regularly, but seemingly randomly, on our build server it does the following:

10:18:08 C:\Program Files (x86)\Jenkins\jobs\******\workspace>Lighthouse.exe "******\Bin\Release\******.xap" "TestResults\******.xml" 
10:18:10 Test Results file name: TestResults\******.xml
10:18:10 Sending signal to Lighthouse Test Executor to start executing tests.
10:21:54 Lighthouse v1.01 (c) 2011 - Remote Unit Test Run Started.
10:21:54 Total Test Assemblies: 1 Total Test Methods: 61.
10:21:55 Testing results saved to file: TestResults\******.xml
10:21:55 Total Tests: 61 | Tests Passed: 0. | Tests Failed: 0
10:21:55 Exiting (-1) because no Unit Tests were executed - this can't be right, right?

So it hangs for about 4 minutes, says the run has started, then runs no test and immediately stops.

I cannot find any clue on what is going wrong-- this also occurs when no other build is running in parallel, and on developers' machines the tests are executed fine. (Update: After a reboot of our build server, the first Lighthouse test failed, and from then on all others seem to succeed. This feeds my suspicion that some process is hanging on to some resource which Lighthouse needs.) (Update: For completeness: Without making any changes to the code or the tests, for me Lighthouse sometimes succeeds and sometimes fails. As can be seen from the console output, it is very likely that Lighthouse does not even start any test: "Tests Passed" and "Tests Failed" are both 0.)

Does anyone have any clue where to start looking for a possible cause?

Thanks!!

(I'm not tagging this question with lighthouse to prevent confusion with more well-known tools of the same name.)

Answer 1

To determine if it is an environmental issue or a code issue, checkout your sourcecode from last month, and run lighthouse multiple times and see how many time the failure occurs.

Perhaps some faulty unit test logic has been checked in?