test: stabilize flaky TestSleep

[flaky-claw]

What problem does this PR solve?

Issue Number: close #69825

Problem Summary:
Flaky test TestSleep in pkg/expression intermittently fails, so this PR stabilizes that path.

What changed and how does it work?

Root Cause

SLEEP(0.01) matched doSleep's 10ms polling interval, so the test sometimes observed timer/ticker ordering instead of kill preservation.

Fix

Raising the test sleep argument to 0.1 keeps the same pending-kill semantics while avoiding the equal-deadline race.

Verification

Spec:

• target: pkg/expression :: TestSleep
• strategy: tidb.go_flaky.default
• plan mode: BASELINE_ONLY
• requirements: required case must execute; no skip; repeat count = 1
• execution surface: GO_TEST_WITH_TAGS
• build tags: intest, deadlock
• baseline gates: required_flaky_gate, build_safety_gate, intent_guard_gate
• feedback surface source: baseline_only

Observed result:

• status: passed
• required case executed: yes
• submission decision: ALLOWED
• note: Required flaky case executed during validation.
  Required flaky case was not skipped.
  target-testsleep passed.
  build passed.
  lint passed.

Gate checklist:

• target-testsleep: PASS
• repeat-testsleep: SKIPPED
• package-raw: SKIPPED
• build: PASS
• lint: PASS

Commands:

• go test -json -tags=intest,deadlock ./pkg/expression -run '^TestSleep$' -count=1
• make build
• make lint

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

Fixes #69825

Summary by CodeRabbit

• Tests
  • Improved test reliability by adjusting timing in sleep-related evaluation tests.
  • Added clarification around polling intervals and deadline behavior.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Details

Needs approval from an approver in each of these files:

• pkg/expression/OWNERS

Approvers can indicate their approval by writing /approve in a comment
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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: ea45807a-a6aa-42ec-aa0f-a3f1d8082541

📥 Commits

Reviewing files that changed from the base of the PR and between 531e40c and eb61fed.

📒 Files selected for processing (1)

• pkg/expression/evaluator_test.go

---

📝 Walkthrough

Walkthrough

TestSleep now uses a 0.1-second strict-model sleep and explains why it remains above the 10ms polling interval while preserving the existing kill-signal assertions.

Changes

TestSleep timing adjustment

Layer / File(s)	Summary
Adjust strict-model sleep timing pkg/expression/evaluator_test.go	The strict-model test changes the sleep duration from 0.01 to 0.1 and adds comments about avoiding polling-interval deadline ties.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested labels: approved, lgtm, ok-to-test, needs-cherry-pick-release-8.5

Poem

I’m a rabbit with timing just right,
No flaky test hops out of sight.
Ten milliseconds below,
Now longer sleeps gently flow,
While the kill signal stays in flight.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately describes the main change: stabilizing flaky TestSleep.
Description check	✅ Passed	The description includes the issue link, problem summary, fix, verification, and checklist items.
Linked Issues check	✅ Passed	The change directly addresses #69825 by fixing the flaky pkg/expression TestSleep case.
Out of Scope Changes check	✅ Passed	The PR only changes the targeted test and related comments, with no unrelated code or scope creep.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="Running error: context loading failed: failed to load packages: failed to load packages: failed to load with go/packages: context deadline exceeded"
level=error msg="Timeout exceeded: try increasing it by passing --timeout option"

---

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.0029%. Comparing base (531e40c) to head (eb61fed).

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #69879        +/-   ##
================================================
- Coverage   76.3207%   74.0029%   -2.3178%     
================================================
  Files          2041       2056        +15     
  Lines        559975     578270     +18295     
================================================
+ Hits         427377     427937       +560     
- Misses       131697     150007     +18310     
+ Partials        901        326       -575     

Flag	Coverage Δ
integration	40.7381% <ø> (+1.0328%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	60.4471% <ø> (ø)
parser	∅ <ø> (∅)
br	47.4060% <ø> (-15.3154%)	⬇️

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