CI failure RegularExpressions didn't throw expected TimeoutException

[noahfalk]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=768415
Build error leg or test failing: System.Text.RegularExpressions.Tests.RegexMatchTests.Match_TestThatTimeoutHappens
Pull request: #106014

Error Message

Assert.Throws() Failure: No exception was thrown
Expected: typeof(System.Text.RegularExpressions.RegexMatchTimeoutException)

{
  "ErrorMessage": "Expected: typeof(System.Text.RegularExpressions.RegexMatchTimeoutException)",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=768415
Error message validated: [Expected: typeof(System.Text.RegularExpressions.RegexMatchTimeoutException)]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 8/7/2024 10:13:42 PM UTC

Report

Build	Definition	Test	Pull Request
772461	dotnet/runtime	System.Text.RegularExpressions.Tests.RegexMatchTests.Match_TestThatTimeoutHappens
769435	dotnet/runtime	System.Text.RegularExpressions.Tests.RegexMatchTests.Match_Timeout_Throws
768415	dotnet/runtime	System.Text.RegularExpressions.Tests.RegexMatchTests.Match_TestThatTimeoutHappens	#106014

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	3	3

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[ericstj]

@stephentoub did we make regex too fast that we need to shorten the timeout?

[stephentoub]

@stephentoub did we make regex too fast that we need to shorten the timeout?

Actually, yes. Though we can't really shorten the timeout, it's already set at 1ms. It's just that a couple of the inputs/patterns being tested now only take around 10ms to run, at least on my machine. If there's any hiccup in CI, things could stretch in a way where it would sporadically pass.

We should just delete these:

runtime/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs

Lines 1267 to 1268 in 68511fd

	yield return new object[] { engine, @"((?!(?>[^a]*))a)+", a1_000_000 };
	yield return new object[] { engine, @"((?<!(?>[^a]*))a)+", a1_000_000 };