Quarantined Tests

March 20, 2026 ยท View on GitHub

Overview

Quarantined tests are tests that are flaky or known to have issues but are not yet fixed. They are marked with the [QuarantinedTest] attribute and are excluded from regular CI runs to prevent false negatives.

How Quarantined Tests Work

The QuarantinedTestAttribute applies the xUnit trait quarantined=true to tests. This trait can then be used with test filters to include or exclude these tests.

Running Tests Without Quarantined Tests

To run tests excluding quarantined tests (this is what CI does):

dotnet test --filter-not-trait "quarantined=true"

Or using the direct test runner:

dotnet exec YourTestAssembly.dll --filter-not-trait "quarantined=true"

Running Only Quarantined Tests

To run only quarantined tests (useful for debugging):

dotnet test --filter-trait "quarantined=true"

Or using the direct test runner:

dotnet exec YourTestAssembly.dll --filter-trait "quarantined=true"

Quarantined Test Lifecycle

  1. Mark as Quarantined: When a test is consistently flaky, mark it with [QuarantinedTest("reason")]
  2. Quarantined Execution: Quarantined tests run automatically in the quarantine CI (every 6 hours)
  3. Fix the Issue: Investigate and fix the underlying issue causing the flakiness
  4. Remove Quarantine: Once fixed and stable, remove the [QuarantinedTest] attribute

Example

[Fact]
[QuarantinedTest("https://github.com/microsoft/aspire/issues/7920")]
public async Task FlakyTest()
{
    // Test implementation
}

CI Integration

  • Regular CI: Uses --filter-not-trait "quarantined=true" to exclude quarantined tests
  • Quarantine CI on Schedule/Push: Runs all quarantined tests twice daily (02:00 and 14:00 UTC) to monitor their status
  • Quarantine CI on Pull Requests: Runs only the first quarantined test project across all OSes (Windows, Linux, macOS) as a sanity check when PRs modify workflow/infrastructure files
  • Results: Quarantined test failures don't block PR merges but are tracked for fixes

For Copilot Agent and Test Runners

When running tests in automated environments like Copilot agent, always use the quarantine filter to avoid false negatives:

# Good - excludes quarantined tests
dotnet test --filter-not-trait "quarantined=true"

# Bad - runs all tests including quarantined ones
dotnet test