*: make TestStores stable

[rleungx]

What problem does this PR solve?

Issue Number: Close #7954.

What is changed and how does it work?

The previously put region does not take effect since it doesn't update the store count.

Check List

Tests

• Unit test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• HuSharp

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[rleungx]

/merge

[ti-chi-bot]

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/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e1e2b18

[codecov]

Codecov Report

Merging #8078 (e1e2b18) into master (22543a9) will increase coverage by 0.03%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

❗ Current head e1e2b18 differs from pull request most recent head 7f851d6. Consider uploading reports for the commit 7f851d6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8078      +/-   ##
==========================================
+ Coverage   77.28%   77.32%   +0.03%     
==========================================
  Files         469      469              
  Lines       61097    61097              
==========================================
+ Hits        47218    47241      +23     
+ Misses      10325    10298      -27     
- Partials     3554     3558       +4     

Flag	Coverage Δ
unittests	77.32% <ø> (+0.03%)	⬆️

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