Running unit tests on more than five cores in parallel

Question

I've followed the instructions on http://blogs.msdn.com/b/vstsqualitytools/archive/2009/12/01/executing-unit-tests-in-parallel-on-a-multi-cpu-core-machine.aspx to the letter and I can execute tests in parallel.

So far so good.

Now the problem: I can't set the parallelTestCount to zero (Auto configure) or to a value above 5. Running five parallel tests works fine but not six.

Yes I have more than five cores on my machine; I am running on an Intel i7 processor which has four cores with hyperthreading meaning I should be able to run 8 tests in parallel.

Now I'm sure there are some other logical or hard limitations and I am not expecting to be able to run on eight cores lightning-speeding eight tests through in parallel.

However it would be cool to know the reason for it not running more than five tests in parallel?

Answer 1

It could just be me but hyperthreading isn't a real core so an i7 only really has 4 physical cores not 8. Maybe it is something to do with that.

Or perhaps there is some bios setting relating to how the hyperthreading can be used by the OS that is preventing it.

Answer 2

It seems that this is a bug in MSTest. I have stumbled upon the same problem, all tests are marked as aborted and there is a "Test run error" link in the Test Results window which if clicked yields this message: "Test run is aborting on '', number of hung tests exceeds maximum allowable '5'".