Fix TestRunDirectories crash on Android with relative/empty paths

[jonathanpeppers]

Continuation of #7772.

On .NET for Android, Assembly.Location returns a relative path like "AndroidTest1.dll" (MonoVM) or an empty string (CoreCLR). Path.GetDirectoryName returns "" for these inputs, and then Directory.CreateDirectory("") throws ArgumentException.

This would fail in Release mode on Android, or if the "fast deployment" feature is disabled.

Guard against empty/relative paths by checking the result of Path.GetDirectoryName and falling back to the standard RootDeploymentDirectory/Out path.

Full stack trace from AZDO build
(https://dev.azure.com/dnceng-public/public/_build/results?buildId=1392743):

INSTRUMENTATION_RESULT: error=System.ArgumentException: The value cannot be an empty string. (Parameter 'path')
 at System.ArgumentException.ThrowNullOrEmptyException(String argument, String paramName)
 at System.ArgumentException.ThrowIfNullOrEmpty(String argument, String paramName)
 at System.IO.Directory.CreateDirectory(String path)
 at Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.Utilities.FileUtility.CreateDirectoryIfNotExists(String directory)
 at Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.Utilities.DeploymentUtilityBase.CreateDeploymentDirectories(IRunContext runContext, String firstTestSource)
 at Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.TestDeployment.Deploy(IEnumerable`1 testCases, IRunContext runContext, IFrameworkHandle frameworkHandle, ITestSourceHandler testSourceHandler, TestRunCancellationToken cancellationToken)
 at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestExecutor.RunTestsAsync(...)
 at Microsoft.VisualStudio.TestTools.UnitTesting.MSTestBridgedTestFramework.SynchronizedRunTestsAsync(...)
 at Microsoft.Testing.Extensions.VSTestBridge.SynchronizedSingleSessionVSTestBridgedTestFramework.ExecuteRequestAsync(...)
 at Microsoft.Testing.Platform.Builder.TestApplication.RunAsync()
 at DotNetNewAndroidTestMonoVM.TestInstrumentation.<OnStart>b__2_0()
INSTRUMENTATION_CODE: 0

Related: dotnet/android#11195 (random PR I saw this), #7769

/cc @nohwnd

[Copilot]

Pull request overview

Fixes an Android-specific crash in MSTest adapter deployment directory creation when Assembly.Location is empty or relative (Android CoreCLR/MonoVM), by ensuring OutDirectory falls back to the standard <RootDeploymentDirectory>\Out path.

Changes:

• Update TestRunDirectories to ignore empty/relative (no directory component) firstTestSource values when computing OutDirectory.
• Add unit tests covering firstTestSource == "" and firstTestSource == "MyTests.dll" fallback behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Adapter/MSTestAdapter.PlatformServices/Deployment/TestRunDirectories.cs	Adds guarded computation of OutDirectory to avoid Directory.CreateDirectory("") on Android scenarios.
test/UnitTests/MSTestAdapter.PlatformServices.UnitTests/Deployment/TestRunDirectoriesTests.cs	Adds regression tests validating fallback behavior for empty/relative firstTestSource.

[Evangelink]

@jonathanpeppers would you mind helping me setup some E2E test for android so we can have something to catch issues/regressions? I am all good with having it as a follow-up.

[Evangelink]

I'm moving forward with a merge, please keep raising issues/PR if you face other problems. I renew my request for some E2E test :)

Thank you!

[jonathanpeppers]

would you mind helping me setup some E2E test for android so we can have something to catch issues/regressions? I am all good with having it as a follow-up.

@Evangelink I wouldn't recommend doing it here, just because booting Android emulators are pretty flaky. We do have an end-to-end test in the Android repo where I found this.

Are the packages here pushed to Maestro/darc? The dotnet/android repo could consume builds weekly (maybe not daily), and that would be pretty easy to setup.

[Evangelink]

Yes, look at the test-tools feed (see https://github.com/microsoft/testfx/blob/main/docs/preview.md)

[jonathanpeppers]

Ok, I see MSTest 4.3.0-preview.26224.2 on the ".NET Core Tooling Dev" darc channel, "test-tools" NuGet feed. I'll give it a try.

[jonathanpeppers]

This will let me dogfood the fix here as well, thanks:

• [tests] Use MSTestPackageVersion in DotNetNewAndroidTest dotnet/android#11209