Test Explorer: MSTest tests not discovered (dotnet test --list-tests emits bare DisplayName, not FQN)

Summary

The Test Explorer discovers tests by scraping dotnet test --list-tests output (test-discovery.ts → parseTestList / isDiscoveredTestLine). That command prints each test's DisplayName, not its FullyQualifiedName. This works for xUnit (whose DisplayName defaults to Namespace.Class.Method) and — after the NUnit.DisplayName=FullName runsettings fix ([TEST-DISCOVERY-NUNIT-FQN]) — for NUnit. MSTest has no such runsettings switch, so its DisplayName stays the bare method name and isDiscoveredTestLine drops it (no .). Result: MSTest tests are not discovered.

Evidence (verified on net10.0, dotnet test --list-tests)

The frameworks e2e suite (test-explorer-frameworks-e2e.test.ts) asserts this current behavior as a regression sentinel.

Fix options (framework-agnostic)

Stop scraping DisplayName text; source TestCase.FullyQualifiedName directly:

• vstest.console.exe --ListFullyQualifiedTests --ListTestsTargetPath:<file> on the built assemblies, or
• the VSTest TranslationLayer (VsTestConsoleWrapper.DiscoverTests) reading TestCase.FullyQualifiedName, or
• a TRX logger and parse FullyQualifiedName from the TRX.

Any of these yields Namespace.Class.Method identically for xUnit, NUnit and MSTest, and would let the NUnit runsettings workaround be removed.

Spec / tracking

• Spec: docs/specs/TESTING-EXPLORER-SPEC.md §2.4 [TEST-DISCOVERY-NUNIT-FQN], §11 Known limitations.
• Plan: docs/plans/TESTING-EXPLORER-PLAN.md.

Start with test-discovery.ts, especially parseTestList and isDiscoveredTestLine, then read test-explorer-frameworks-e2e.test.ts and the referenced testing explorer spec and plan. Compare the available discovery approaches in the issue and trace how test names reach Test Explorer. Done means MSTest, xUnit, and NUnit tests are discovered by fully qualified name and the regression coverage reflects the corrected behavior.