test: stabilize flaky TestTTLStatusCache/last_job_finish_time

[flaky-claw]

What problem does this PR solve?

Issue Number: close #69619

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

What changed and how does it work?

Root Cause

TestTTLStatusCache used CreateMockStoreAndDomain, which starts the background TTL job manager in the test environment. After the TTL manager becomes leader, it may immediately run DoGC().

The subtests in TestTTLStatusCache insert temporary rows into mysql.tidb_ttl_table_status and previously relied on rows from earlier subtests remaining in the table. However, those rows have current_job_status IS NULL, so they can be removed by the background TTL table-status GC during the test.

As a result, later subtests may observe fewer rows than expected, making the original cumulative assertion (len(isc.Tables) == index+1) flaky.

Fix

Clearing the TTL status table inside each field subtest makes each field extraction case self-contained.

Verification

Spec:

• target: pkg/ttl/cache :: TestTTLStatusCache/last_job_finish_time
• 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:

• native_repro: SKIPPED
• target_flaky_validation: PASS
• package_validation: PASS
• build_safety: BLOCKED
• ready_lint: BLOCKED
• prow_bazel_shard: SKIPPED

Commands:

• go test -json -tags=intest,deadlock ./pkg/ttl/cache -run '^TestTTLStatusCache/last_job_finish_time$' -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 #69619

Summary by CodeRabbit

• Tests
  • Updated cache test coverage to reset table status data between subtests.
  • Strengthened assertions so each case checks a single cached table consistently, improving test reliability.

[ti-chi-bot]

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[coderabbitai]

📝 Walkthrough

Walkthrough

Modified TestTTLStatusCache in pkg/ttl/cache/ttlstatus_test.go to delete existing rows from mysql.tidb_ttl_table_status before each subtest's insert, fixed the expected cache count to 1 per subtest, and added a nil guard before asserting the retrieved table's fields.

Changes

TTL status cache test fix

Layer / File(s)	Summary
Reset table state per subtest pkg/ttl/cache/ttlstatus_test.go	Test now clears mysql.tidb_ttl_table_status before inserting each per-field row, expects exactly 1 cached table (instead of accumulating), and only runs the field assertion when the retrieved table is non-nil.

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

Possibly related PRs

• pingcap/tidb#68701: Both PRs modify pkg/ttl/cache tests by manipulating mysql.tidb_ttl_table_status rows for deterministic TTL test behavior.

Suggested labels: approved, lgtm

Suggested reviewers: lcwangchao, YangKeao

Poem

A rabbit hopped through flaky rows,
Cleared the table, tidy goes,
One test, one row, no more chaos,
NotNil guards where doubt arose,
Hop hop, the cache now steady flows! 🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes address issue #69619 by removing shared-state dependence in TestTTLStatusCache/last_job_finish_time.
Out of Scope Changes check	✅ Passed	The PR is limited to the targeted test stabilization and does not introduce unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly describes the main change: stabilizing a flaky TTL status cache test.
Description check	✅ Passed	The description matches the template and includes the issue, problem summary, fix details, checklist, and release note section.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.1105%. Comparing base (8be4bd0) to head (26c741e).

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #69635        +/-   ##
================================================
- Coverage   76.3268%   74.1105%   -2.2164%     
================================================
  Files          2041       2050         +9     
  Lines        560589     576524     +15935     
================================================
- Hits         427880     427265       -615     
- Misses       131808     149053     +17245     
+ Partials        901        206       -695     

Flag	Coverage Δ
integration	40.6942% <ø> (+0.9890%)	⬆️

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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