test: fix unstable unit test TestScaleNode

[wk989898]

What problem does this PR solve?

Issue Number: close #4837

What is changed and how it works?

TestScaleNode no longer assumes that a NodeManager.Tick has already completed all coordinator bootstrap side effects. After adding
nodes, the test now waits until the new nodes are initialized in the coordinator bootstrapper before asserting the 2/2/2 distribution. After removing a node, it waits until that
node has been removed from bootstrap tracking before asserting the 3/3 distribution

Check List

Tests

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

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

If you don't think this PR needs a release note then fill it with `None`.

Summary by CodeRabbit

• Tests
  • Improved node-scaling tests to wait for and assert bootstrapper state changes: verifies nodes become initialized after addition and are removed after deletion, using timed polling to ensure reliable membership checks.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign asddongmen for approval. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a40e4880-38f9-480e-85ae-24bbeddbd1d7

📥 Commits

Reviewing files that changed from the base of the PR and between 77749f6 and 70575df.

📒 Files selected for processing (1)

• coordinator/coordinator_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• coordinator/coordinator_test.go

---

📝 Walkthrough

Walkthrough

TestScaleNode now waits for coordinator.bootstrapper state changes after node additions and removals: it polls NodeInitialized for newly added node IDs and verifies removed node IDs are absent. Two local helpers using require.Eventually implement the polling.

Changes

Bootstrap State Verification in TestScaleNode

Layer / File(s)	Summary
Bootstrap state verification in TestScaleNode coordinator/coordinator_test.go	After adding maintainer nodes, the test waits until those node IDs are marked initialized by coordinator.bootstrapper (requireBootstrapReady). After removing a node, it waits until that node ID is no longer present in the bootstrapper (requireBootstrapNodeRemoved). Both helpers use require.Eventually to poll NodeInitialized / HasNode.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested labels

lgtm, approved, size/XS, release-note-none

Suggested reviewers

• tenfyzhong
• lidezhu

Poem

🐰 I hopped in tests where nodes would play,
I waited patiently for states to say,
"Initialized" chimed for each new friend,
And gone were nodes that met their end.
A small, steady check — now tests can stay.

🚥 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 accurately describes the main change: fixing an unstable unit test TestScaleNode by adding proper synchronization for bootstrap operations.
Description check	✅ Passed	The description provides issue number, explains what changed and how it works, and addresses the template sections. The release note is not filled but the template allows for flexibility.
Linked Issues check	✅ Passed	The PR directly addresses issue #4837 by adding bootstrap-aware assertions that eliminate timing assumptions, making TestScaleNode deterministic and stable in CI.
Out of Scope Changes check	✅ Passed	All changes are scoped to stabilizing TestScaleNode through bootstrap synchronization helpers; no unrelated modifications are present.

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

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch wk989898-patch-6

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[gemini-code-assist]

Code Review

This pull request introduces helper functions requireBootstrapReady and requireBootstrapNodeRemoved in coordinator_test.go to ensure proper synchronization during node scaling tests. These helpers are integrated into TestScaleNode to verify node initialization and removal before checking replication sizes. There are no review comments, and I have no additional feedback to provide.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.