Mark specification test projects as non-test projects

[roji]

Our specification test projects aren't actual test projects in the sense that tests should be run in them directly; they're there so that providers can extend them, and those concrete test projects are indeed "runnable" test projects.

As things are, e.g. VS Code needlessly attempts to perform test discovery on the specification projects and triggers the following:

Error:
  An assembly specified in the application dependencies manifest (Microsoft.EntityFrameworkCore.Specification.Tests.deps.json) was not found:
    package: 'Castle.Core', version: '5.2.1'
    path: 'lib/net6.0/Castle.Core.dll'
Testhost process for source(s) '/Users/roji/projects/efcore/artifacts/bin/EFCore.Specification.Tests/Debug/net11.0/Microsoft.EntityFrameworkCore.Specification.Tests.dll' exited with error: Error:
  An assembly specified in the application dependencies manifest (Microsoft.EntityFrameworkCore.Specification.Tests.deps.json) was not found:
    package: 'Castle.Core', version: '5.2.1'
    path: 'lib/net6.0/Castle.Core.dll'
. Please check the diagnostic logs for more information.
  EFCore.Specification.Tests test net11.0 failed with 1 error(s) (0.2s)

(this can also be triggered simply by running dotnet test on the EFCore.Specification.Tests). I also suspect this may be slowing test discovery considerably as EFCore.Specification.Tests is huge, but doesn't actually contain (runnable) tests.

This adds <IsTestProject> to prevent detecting these projects as test projects.

[Copilot]

Pull request overview

This PR prevents test discovery on specification test projects by marking them with <IsTestProject>false</IsTestProject>. Specification test projects contain abstract base test classes that are extended by provider-specific test projects, but are not meant to be run directly. Currently, tools like VS Code attempt test discovery on these projects, which fails with dependency errors (e.g., Castle.Core assembly not found) and unnecessarily slows down test discovery.

Changes:

• Added <IsTestProject>false</IsTestProject> to EFCore.Specification.Tests and EFCore.Relational.Specification.Tests
• Commented out xunit.runner.visualstudio package reference in EFCore.Specification.Tests (test runner not needed for non-runnable projects)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
test/EFCore.Specification.Tests/EFCore.Specification.Tests.csproj	Added IsTestProject=false and commented out xunit.runner.visualstudio package reference
test/EFCore.Relational.Specification.Tests/EFCore.Relational.Specification.Tests.csproj	Added IsTestProject=false property