test: stabilize flaky TestTTLStatusCache/last_job_ttl_expire

[flaky-claw]

What problem does this PR solve?

Issue Number: close #69621

Problem Summary:
Flaky test TestTTLStatusCache/last_job_ttl_expire in pkg/ttl/cache intermittently fails, so this PR stabilizes that path.

What changed and how does it work?

Root Cause

TestTTLStatusCache assumed sibling subtests always ran before the selected subtest, so filtered/sharded execution made cumulative length assertions invalid.

Fix

Clearing the TTL status table per subtest makes each field-decoding check independent while preserving the exact decoded-field assertions.

Verification

Spec:

• target: pkg/ttl/cache :: TestTTLStatusCache/last_job_ttl_expire
• strategy: tidb.issue_scoped.v2
• 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: failed
• required case executed: yes
• submission decision: ALLOWED
• note: Required flaky case executed during validation.
  Required flaky case was not skipped.
  target_flaky_validation passed.
  package_validation passed.

Gate checklist:

• pre_fix_native_repro: SKIPPED
• target_flaky_validation: PASS
• package_validation: PASS
• build_gate: BLOCKED
• ready_lint: BLOCKED

Commands:

• go test -json -tags=intest,deadlock ./pkg/ttl/cache -run '^TestTTLStatusCache/last_job_ttl_expire$' -count=1
• go test -json -tags=intest,deadlock ./pkg/ttl/cache -count=1

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 #69621

Summary by CodeRabbit

• Tests
  • Improved TTL cache test coverage by isolating each field case and verifying the cache contains a single expected entry after each update.
  • Added a safety check before validating cached table data, making the test more robust and easier to diagnose if it fails.

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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: 4751c9ca-5902-4c01-a91f-7c2a4bad6c15

📥 Commits

Reviewing files that changed from the base of the PR and between 8be4bd0 and a890fef.

📒 Files selected for processing (1)

• pkg/ttl/cache/ttlstatus_test.go

---

📝 Walkthrough

Walkthrough

The test TestTTLStatusCache was updated to clear the mysql.tidb_ttl_table_status table before each subtest's row insertion, then assert the cache contains exactly one entry with a nil-check before running field-specific assertions, replacing the previous cumulative index-based checks.

Changes

TTL status cache test fix

Layer / File(s)	Summary
Clear table and assert single entry per subtest pkg/ttl/cache/ttlstatus_test.go	Each subtest now clears the status table before inserting its row, asserts exactly one cache entry, and retrieves it into a nil-checked variable before the field assertion.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• pingcap/tidb#67243: Updates TTL status cache assertions by clearing/re-reading mysql.tidb_ttl_table_status entries in TestTTLStatusCache.

Suggested labels: ok-to-test, approved, lgtm

Suggested reviewers: lcwangchao, YangKeao

Poem

A hop, a clear, a fresh new row,
No stale old data left to grow.
One table found, checked nice and tight,
No more flaky tests at night.
🐇✨ Clean cache, delight!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: stabilizing a flaky TTL cache test.
Description check	✅ Passed	The description includes the issue link, problem summary, root cause, fix, verification, checklist, and release note.
Linked Issues check	✅ Passed	The change addresses issue #69621 by making TestTTLStatusCache/last_job_ttl_expire independent and removing the flaky cumulative assumption.
Out of Scope Changes check	✅ Passed	The PR only modifies the targeted test to fix flakiness and does not introduce unrelated changes.
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 74.1091%. Comparing base (8be4bd0) to head (a890fef).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #69647        +/-   ##
================================================
- Coverage   76.3268%   74.1091%   -2.2178%     
================================================
  Files          2041       2050         +9     
  Lines        560589     576524     +15935     
================================================
- Hits         427880     427257       -623     
- Misses       131808     149060     +17252     
+ Partials        901        207       -694     

Flag	Coverage Δ
integration	40.6921% <ø> (+0.9868%)	⬆️

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	47.4650% <ø> (-15.2563%)	⬇️

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