How can a non-test class-library reference IXunitTestCaseDiscoverer in v3?

[martin-tnc]

The problem

• We have built an internal logging/extensibility library that wraps xUnit.
• In xUnit v2 we referenced xunit.extensibility.core/execution and implemented our own
  IXunitTestCaseDiscoverer.
• After upgrading to v3.1. I can no longer compile because the interface
  only exists in xunit.v3.core, and that package now forces the project to be an
  <OutputType>Exe</OutputType> test project.

I’ve read #3157 and the package-layout doc, and I understand that library projects should now reference xunit.v3.extensibility.core instead of xunit.v3.core.
Unfortunately, that package does not appear to surface IXunitTestCaseDiscoverer (or any of the discovery interfaces).

What I’ve tried / references

• xUnit.net v3 test projects must be executable #3157 explains the package split, but the guidance assumes the interface is available via xunit.v3.extensibility.core.
• xunit.v3.extensibility.core and IXunitTestCaseDiscoverer, etc... #3225 was closed with a similar suggestion, but I still cannot find the type after switching to that package. 
• Package docs: https://xunit.net/docs/nuget-packages-v3 (no luck).

Questions

• Which package is intended to expose IXunitTestCaseDiscoverer (and friends) for library authors in v3?
• If it should come from xunit.v3.extensibility.core, is the interface perhaps marked internal by mistake, or missing a type-forward?
• Is there an official way to suppress the build-time “must be executable” check when xunit.v3.core is referenced from a class-library (e.g., an IsTestProject MSBuild property)?

Many thanks for any pointers.

[svenah]

Yes, definitely more thorough explanation, but exact same issue!

[bradwilson]

I cannot repro this.

[bradwilson]

Please provide your repro project.

[bradwilson]

Just to be clear about what exists in which package...

xunit.v3.core.dll does not exist in the xunit.v3.core NuGet package:

It lives in the xunit.v3.extensibility.core package:

This is done via dependency. When you reference xunit.v3.core, among the other things it brings with it is a package dependency on xunit.v3.extensibility.core so that you get the DLL to link against:

[martin-tnc]

This was helpful, thanks. Please close the issue.