[akirayamamoto]

Why

Windows CI sometimes fails a test that actually passed, during cleanup:

System.Exception : Failed to remove C:\Users\cloudtest\AppData\Local\Temp\InstallScript-Tests\5gd5sltz.wbx
---- System.UnauthorizedAccessException : Access to the path 'dotnet.exe' is denied.

Seen in #659 and again on #743 (WhenInstallingASpecificVersionOfDotnetRuntime, 7.0.0-alpha). #660 made the error visible but didn't stop it.

Root cause

Each test runs dotnet --info from its install folder, then Dispose() deletes that folder. Windows can keep dotnet.exe locked for a moment after the process exits (for example while antivirus scans it), so the first delete attempt can fail.

Approach

• Moved the cleanup into TestUtils.DeleteInstallationDirectory.
• It retries the delete on UnauthorizedAccessException or IOException (file in use), up to 8 attempts. The wait doubles from 100 ms and is capped at 1 s, so it gives up after about 4.5 s. Then it throws the same "Failed to remove" error as before.
• A missing folder is still ignored, as before.

Validation

I reproduced the failure on a Windows GitHub Actions runner in my fork with a temporary test that deletes the folder while a copied executable is still running from it:

• Without the retry: fails with the same Access to the path 'dotnet.exe' is denied error.
• With the retry: passes.

I left that test out of this PR, since the suite doesn't test its own helpers.

Follow-up to #659

🤖 Generated with Claude Code

[akirayamamoto]

Hi @ellahathaway and @MichaelSimons, this one is small and CI is green.

It retries the test folder cleanup when Windows still has dotnet.exe locked, which is the flaky failure blocking #743 (fix "Killed: 9" on macOS). Merging this first should get #743 green too.

Thanks!

[MichaelSimons]

Hi @ellahathaway and @MichaelSimons, this one is small and CI is green.

It retries the test folder cleanup when Windows still has dotnet.exe locked, which is the flaky failure blocking #743 (fix "Killed: 9" on macOS). Merging this first should get #743 green too.

Thanks!

@akirayamamoto , thanks for your contribution. @dotnet/install-scripts-maintainers is the team to ping for approval or other questions. @ellahathaway and myself, are focusing in different areas at the moment.