pkg/server: stabilize flaky TestIssue54335

[flaky-claw]

What problem does this PR solve?

Issue Number: close #67558

Problem Summary:
Flaky test TestIssue54335 in pkg/server intermittently fails, so this PR stabilizes that path.

What changed and how does it work?

Root Cause

TestIssue54335 constructed a client connection with nil pkt and relied on failpoint behavior; when the query reached result writing, writePacket dereferenced nil and panicked.

Fix

Initializing cc.pkt in the flaky test removes the nil dereference window without changing product behavior.

Verification

Spec:

• target: pkg/server :: TestIssue54335
• strategy: tidb.go_flaky.default
• plan mode: BASELINE_ONLY
• requirements: required case must execute; no skip; repeat count = 1
• baseline gates: required_flaky_gate, build_safety_gate, intent_guard_gate

Observed result:

• status: passed
• required case executed: yes
• submission decision: ALLOWED
• scope debt present: yes

Gate checklist:

• Required flaky gate: PASS
• Build safety gate: PASS
• Intent guard gate: PASS
• Repo-wide advisory gate: SKIPPED
• Feedback specific gate: SKIPPED

Commands:

• go test -json ./pkg/server -run '^TestIssue54335$' -count=1
• go test -json ./pkg/server -count=1
• make build

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 #67558

Summary by CodeRabbit

• Tests
  • Refactored connection test implementation to leverage dedicated test session creation and management with improved session initialization patterns and handling approaches.
  • Enhanced client connection initialization process with explicit packet IO handler configuration and setup for improved test isolation and reliability.
  • Upgraded test infrastructure architecture to strengthen overall maintainability, consistency, and reliability of test execution.

[pantheon-ai]

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[tiprow]

Hi @flaky-claw. Thanks for your PR.

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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: 13867fd9-bc15-4859-91ff-c213cae7dcb2

📥 Commits

Reviewing files that changed from the base of the PR and between ce92298 and 950f931.

📒 Files selected for processing (1)

• pkg/server/conn_test.go

---

📝 Walkthrough

Walkthrough

The pull request refactors a flaky test TestIssue54335 in pkg/server/conn_test.go to use a dedicated test session created via session.CreateSession4Test(store) instead of TestKit's session, and explicitly initializes the packet IO for the manually constructed clientConn to avoid nil references.

Changes

Cohort / File(s)	Summary
Test Session Refactoring pkg/server/conn_test.go	Replaced TestKit session usage with session.CreateSession4Test(store) to manage session lifecycle; updated TiDBContext initialization and added explicit packet IO initialization (internal.NewPacketIOForTest) to prevent nil references in manually constructed clientConn.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• #67243 — Refactors tests to replace TestKit sessions with internal test sessions (session.CreateSession4Test) to avoid race conditions in similar test patterns.

Suggested labels

contribution, size/XS, ok-to-test, approved, lgtm

Suggested reviewers

• YangKeao
• lcwangchao

Poem

🐰 A flaky test once danced around,
With TestKit sessions all unbound,
But now with sessions pure and true,
And packet IO shining new,
Stability's our proud pursuit! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'pkg/server: stabilize flaky TestIssue54335' accurately describes the main change—fixing a flaky test in the pkg/server package.
Description check	✅ Passed	The description addresses the template requirements: issue number is provided (close #67558), problem is clearly explained (nil pkt dereference), solution is described, testing is documented (unit test), and release note is included.
Linked Issues check	✅ Passed	The PR directly addresses issue #67558 by identifying and fixing the root cause of the flaky test (nil pkt dereference) and includes verification that the test now passes.
Out of Scope Changes check	✅ Passed	All changes are within scope—modifications are limited to stabilizing TestIssue54335 by initializing cc.pkt and using a dedicated test session without introducing unrelated functionality.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ 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 77.4293%. Comparing base (e3f45e4) to head (950f931).
⚠️ Report is 29 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #67888        +/-   ##
================================================
- Coverage   77.7969%   77.4293%   -0.3677%     
================================================
  Files          1983       1966        -17     
  Lines        548948     549053       +105     
================================================
- Hits         427065     425128      -1937     
- Misses       120962     123923      +2961     
+ Partials        921          2       -919     

Flag	Coverage Δ
integration	40.9074% <ø> (+1.1101%)	⬆️
unit	76.6556% <ø> (+0.3061%)	⬆️

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

Components	Coverage Δ
dumpling	61.5065% <ø> (ø)
parser	∅ <ø> (∅)
br	50.0872% <ø> (-13.0244%)	⬇️

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[yinsustart]

/retest

[tiprow]

@yinsustart: PRs from untrusted users cannot be marked as trusted with /ok-to-test in this repo meaning untrusted PR authors can never trigger tests themselves. Collaborators can still trigger tests on the PR using /test.

Details

In response to this:

/retest

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[xzhangxian1008]

lgtm

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wshwsh12, xzhangxian1008

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Details

Needs approval from an approver in each of these files:

• OWNERS [wshwsh12]

Approvers can indicate their approval by writing /approve in a comment
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-04-21 08:32:42.192163656 +0000 UTC m=+2068367.397523703: ☑️ agreed by wshwsh12.
• 2026-04-23 02:14:51.211476875 +0000 UTC m=+2218496.416836922: ☑️ agreed by xzhangxian1008.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #70014.
But this PR has conflicts, please resolve them!