Each unit test project runs on a different AppDomain. I modified the above calls to write the 
```
AppDomain.CurrentDomain.Id
```

On my machine
* AutoFixtureUnitTest runs on AppDomain Id=2 
* AutoFixture.Xunit.UnitTest project runs on AppDomain Id=4

That's great, IMHO as it provides the isolation we need among xUnit.net versions.