Honor Timeout on StaFact/StaTheory and other UI test attributes

[Copilot]

Timeout had no effect on StaFact, StaTheory, or the other UI fact/theory attributes. A test like this never failed:

[StaFact(Timeout = 1000)]
public void TimeoutTest() => Thread.Sleep(2000);

There were two causes. Facts dropped the value during discovery. On top of that, nothing enforced timeouts for either facts or theories.

Changes

• Discovery (Utilities.CreateTestCasesForFact)
  • Now passes details.Timeout to UITestCase. The theory paths already did this.
• Execution (UITestRunner.RunTest)
  • This method fully overrides xunit's CoreTestRunner.RunTest, where RunTestWithTimeout lives, so timeouts were never applied. The xunit behavior is now reimplemented here:
    • The test races Task.Delay(timeout). If the delay wins, the runner records a TestTimeoutException, updates the test context, and calls TestContext.Current.CancelCurrentTest().
    • When a timeout is set, the test is posted to the UI thread instead of invoked inline. Otherwise a test that blocks the thread synchronously, such as with Thread.Sleep, would keep the runner from ever reaching the timeout check.
    • The delay timer is cancelled once the test completes.
    • As in xunit, the timeout is skipped when a debugger is attached.

Behavior worth reviewing

• Timed-out tests keep running. As in xunit, the result is reported without waiting for the test. A test that ignores the cancellation token keeps occupying its UI thread. Later work that needs that thread waits behind it: a MaxAttempts retry, a culture restore, or tests sharing the thread through a UIThreadFixtureBase fixture.
• Late reports for blocking UIFact tests. These tests use a sync context set as current on the UI thread. If such a test blocks that thread, the timeout is recorded, but the failure is only reported once the thread frees up, because the outer pipeline resumes on that context.

Tests

• Timeout_NotExceeded (fact and theory): checks that the timeout reaches the test case and that the ctor and test thread/sync context stay the same on the new posted path.
• Timeout_Exceeded_Sync / Timeout_Exceeded_Async (fact and theory): tagged FailureExpected, so CI skips them. They cover a test that blocks the thread and an async one.

• Fixes Timeout parameter for StaFact and StaTheory has no effect in version 4.0.23 #236

[AArnott]

@copilot retarget this change to the v4.0 branch.

[Copilot]

@copilot retarget this change to the v4.0 branch.

I couldn't retarget this PR. I can't change a PR's base branch, and my push tool can't force-push. Rebasing this branch onto v4.0 needs a force-push, because main is 55 commits ahead of v4.0. If you switch the base in the UI as-is, those commits will show up in the diff.

I did check the port locally:

• Discovery: v4.0 already passes Timeout in CreateTestCaseForFact, so the Utilities.cs change isn't needed there.
• What's needed: only the UITestRunner.cs timeout enforcement and the new tests.
• Results: with ffcd6a3 and ec232ce cherry-picked onto origin/v4.0, keeping v4.0's Utilities.cs on conflict, the build has no errors. The non-FailureExpected tests pass on net8.0, and the timeout tests fail by timing out after about 100ms.

You can do either of these:

• Cherry-pick ffcd6a3 and ec232ce onto a branch off v4.0 and open a PR from it. I can't open PRs.
• Force-push a rebased branch here yourself, then switch the base to v4.0.

This PR is unchanged and still targets main.

[Copilot]

Copilot review overview

🟡 Changes recommended

Constructors remain outside timeout enforcement, and timeout failures are excluded from automated CI coverage.

Review effort: Balanced
Findings: 1 · 2

Open (3)

• Timeout excludes async fixture initialization · New
• Excluded test leaves synchronous timeout path untested · New
• Excluded theory leaves timeout enforcement untested · New

What changed in this PR

Adds timeout enforcement for UI-based facts and theories.

Changes:

• Propagates fact timeout metadata during discovery.
• Races UI-thread execution against the configured timeout.
• Adds timeout and thread-affinity tests.

File	Description
src/​Xunit.StaFact/​Sdk/​Utilities.cs	Preserves fact timeout values.
src/​Xunit.StaFact/​Sdk/​UITestRunner.cs	Implements timeout execution and cancellation.
test/​Xunit.StaFact.Tests/​UIFactTests.cs	Adds fact timeout scenarios.
test/​Xunit.StaFact.Tests/​UITheoryTests.cs	Adds theory timeout scenarios.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.30435% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.34%. Comparing base (90275fd) to head (87c3413).

Files with missing lines	Patch %	Lines
src/Xunit.StaFact/Sdk/UITestRunner.cs	89.74%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             v4.0     #237      +/-   ##
==========================================
+ Coverage   83.94%   85.34%   +1.39%     
==========================================
  Files          36       36              
  Lines         760      805      +45     
  Branches       64       69       +5     
==========================================
+ Hits          638      687      +49     
+ Misses        100       95       -5     
- Partials       22       23       +1     

Flag	Coverage Δ
Linux	82.76% <91.30%> (+1.78%)	⬆️
Windows	81.24% <91.30%> (+1.63%)	⬆️
macOS	82.76% <91.30%> (+1.78%)	⬆️

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