Debugging Workflow

[jaredpar]

The out of process support is functional now but the current design isn't going to work well for debugging unit tests. The current work flow is to create a new process per assembly per UI invocation of running tests. This makes attach pretty difficult from Visual Studio.

I think we need to move to a slightly different model for running tests. Essentially move the worker process into a more long term server role. Visual Studio can attach to this process and have a natural experience for debugging unit tests.

The xunit framework still uses AppDomain for isolating test runs so the process shouldn't lock the DLLs on disk once the run is completed.

[Pilchie]

If it doesn't lock long term, why do we need the other process at all?

[jaredpar]

Couple of reasons:

• A process model is the only path forward for us to run both desktop and CoreCLR tests from the same runner.
• AppDomains don't protect the UI against stack overflow, AV, deadlock, native resource leaks, etc ...
• Test run cancellation is much more reliable in a process model. In a pinch it can be implemented as "kill the worker process".

Note that my above about AppDomains not locking long term is part speculation. I assume it will give us the intended behavior here but I don't actually know. Part of the reason I filed this issue is to investigate if this is viable or not.