Appdomain.Unload occasionally ends up hanging the test run

[AbhitejJohn]

Description

We've seen instances where test code that isn't properly cleaned up, ends up hanging the finalizer thread when AppDomain.Unload gets called. From msdn an AD.Unload could take an indeterminate amount of time to return in cases like these. We should have some kind of a timeout for this operation so we do not hang forever which especially impacts CI runs.

Environment

Latest version of the adapter.

[codito]

This issue needs to be fixed in MSTest v1 and v2.

[AbhitejJohn]

We've seen this happen for users having an app.config file. Here is a workaround for such users:
Add the following startup section to the config

<configuration>
…
              <startup useLegacyV2RuntimeActivationPolicy="true">
                            <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0" />
              </startup>
…
</configuration>

[acesiddhu]

RFC for the change we did https://github.com/Microsoft/vstest-docs/blob/master/RFCs/0019-Disable-Appdomain-While-Running-Tests.md

Closing this issue