test: Upgrade to xUnit v3 and mtp v2

[benjiro]

This PR

This PR upgrades the test infrastructure to use xUnit v3 and Microsoft.Testing.Platform (mtp) v2, modernizing the testing framework across all test projects in the dotnet-sdk.

• Upgrades xUnit to v3
• Upgrades Microsoft.Testing.Platform to v2
• Updates all test projects to use the new testing framework versions
• Refactors test assertions and lifecycle management to be compatible with xUnit v3 APIs
• Updates Directory.Packages.props with new package versions
• Adds global.json configuration

Related Issues

Fixes #624
Fixes #648

Notes

This is a significant infrastructure upgrade that affects all test projects:

• OpenFeature.E2ETests
• OpenFeature.Hosting.Tests
• OpenFeature.IntegrationTests
• OpenFeature.Providers.MultiProvider.Tests
• OpenFeature.Tests

The changes include updates to test lifecycle management and assertion patterns to align with xUnit v3 conventions. Net reduction of ~40 lines of code across the test suite while maintaining all existing test coverage.

How to test

1. Clone the repository
2. Run dotnet test to execute the full test suite
3. Verify all tests pass with the new xUnit v3 and mtp v2 framework
4. Check that test output and reporting work as expected

[gemini-code-assist]

Summary of Changes

Hello @benjiro, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request delivers a significant infrastructure upgrade by migrating the entire test suite to xUnit v3 and Microsoft.Testing.Platform v2. This modernization effort involves updating package dependencies, adjusting project configurations, and refactoring asynchronous test logic to incorporate cancellation tokens and optimized async return types. The changes aim to enhance the robustness, maintainability, and performance of the testing framework without altering existing test coverage.

Highlights

• Testing Framework Upgrade: The test infrastructure has been upgraded to xUnit v3 and Microsoft.Testing.Platform (mtp) v2, modernizing the entire testing framework across all test projects.
• Package Version Updates: Key testing-related package versions have been updated in Directory.Packages.props, including Reqnroll.xunit.v3, xunit.v3.mtp-v2, and xunit.runner.visualstudio.
• Test Project Configuration: All test projects (.csproj files) now include <OutputType>Exe</OutputType> and reference the new xUnit v3 packages. A global.json entry has been added to configure Microsoft.Testing.Platform as the test runner.
• Asynchronous API Refactoring: Numerous asynchronous methods across test files, including provider initialization, shutdown, flag resolution, and hook executions, have been updated to explicitly accept and utilize CancellationToken parameters, aligning with modern async patterns and xUnit v3's TestContext.Current.CancellationToken.
• Test Assertion and Lifecycle Changes: Specific test assertion patterns have been refactored, such as changing Skip.If to Assert.SkipWhen. Additionally, IAsyncLifetime methods (InitializeAsync, DisposeAsync) in test fixtures now return ValueTask instead of Task for improved performance.

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[gemini-code-assist]

Code Review

This pull request successfully upgrades the test infrastructure to xUnit v3 and Microsoft.Testing.Platform v2. The changes are extensive and consistently applied across all test projects, including updating package versions, project files, and test code to use new APIs and propagate cancellation tokens. This is a solid modernization of the test suite. I have a couple of suggestions to improve test correctness and maintainability.

[askpt]

@benjiro are you still working on this task? The xunit library is now officially deprecated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.08%. Comparing base (f875bc3) to head (298db6c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #681      +/-   ##
==========================================
- Coverage   93.52%   93.08%   -0.45%     
==========================================
  Files          69       65       -4     
  Lines        2981     2935      -46     
  Branches      355      355              
==========================================
- Hits         2788     2732      -56     
- Misses        135      140       +5     
- Partials       58       63       +5     

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[benjiro]

Had to dust off my old windows box to debug the code coverage issue was a curly one. Seems that GithubActionLogger is interacting with Coverlet. Had to add --coverlet-exclude "[GitHubActionsTestLogger*]*" so Coverlet doesn't try to instrument it. Running dotnet test will run e2e test project since submodule stuff isn't bootstrapped in code coverage workflow had to add --ignore-exit-code 8 not fail on zero test projects

Due to the upgrade to the MTP and coverage system there is a slight discrepancy overall code coverage

[askpt]

Have a look into the package I referenced. I believe it can be removed. Other than that, LGTM!

[toddbaert]

Thanks @benjiro . Approved with a very small nit.

Consider @askpt 's points.