posts/dotnet-10-testing/

[giscus[bot]]

posts/dotnet-10-testing/

.NET 10 replaces VSTest with Microsoft.Testing.Platform, bringing SDK-integrated testing with faster discovery, consistent behavior across …

https://daily-devops.net/posts/dotnet-10-testing/

[seangwright]

Thanks for this overview. I've been stepping into MTP to make sure my .NET 10 project is always adopting the current best practices. It already uses:

• CPM to prevent package version conflicts across the solution
• global.json for consistent SDK experiences
• Directory.Build.props and Directory.Build.targets for centralized build configuration

I felt MTP was finally ready to adopt as well. It... mostly is.

The main issue is documentation. There is a 20 year history of VSTest test configuration, old CI tricks, dotnet test, and NUnit/Xunit/MSTest configuration differences in documentation across blogs, GitHub, and learn.microsoft.com. This makes it difficult to identify exactly what is and what isn't possible and correct when adopting MTP.

Your tip to explicitly global.json in CI configuration is very important and something I see many projects still not adopting. I think teams still don't understand why global.json is important for their projects.

And here’s the part Microsoft doesn’t emphasize: MTP won’t save you from bad tests. If your test suite is flaky, brittle, or poorly isolated, the new platform just runs that mess faster.

One exception to this is the change in how ignored tests are treated for the final exit code of a dotnet test run. In the past this would not fail the test run, but with MTP it does! The team behind MTP wanted developers to clearly opt-in to ignoring tests as "ok".

The MTP dotnet test exit codes are documented here https://learn.microsoft.com/en-us/dotnet/core/testing/microsoft-testing-platform-exit-codes.

What this means if you want to run dotnet test on your solution file but skip your long-running E2E tests via a *.runsettings configuration file, you will need to tell MTP to ignore exit code 8 (skipped tests) as an error:

dotnet test --settings ./test/basic.runsettings -p:TestingPlatformCommandLineArguments="--ignore-exit-code 8"

In this case, my basic.runsettings looks like this:

<RunSettings>
    <!-- General run configuration -->
    <RunConfiguration>
        <!-- https://learn.microsoft.com/en-us/dotnet/core/testing/selective-unit-tests?pivots=nunit#nunit-examples -->
        <TestCaseFilter>FullyQualifiedName!~E2E.Tests</TestCaseFilter>
    </RunConfiguration>
</RunSettings>

Yes, I could use the MTP --filter option instead but my E2E tests have a separate .runsettings with a Playwright configuration section. So, I decided to use .runsettings for both sets of tests.

[samtrion]

Thanks for highlighting these real-world details, especially the exit code change for skipped tests. You’re right: MTP finally enforces configuration discipline, but the documentation gap between VSTest-era advice and the new platform is still a problem. The new exit code behavior (8 for skipped) is a breaking change for many CI setups, and --ignore-exit-code 8 is now essential if you filter tests via .runsettings or CLI parameters.

Bottom line: MTP brings predictability, but only if teams update both their configs and their habits. Sharing these migration lessons is what actually moves the ecosystem forward. Thanks for adding yours!