[ISSUE #8421]add more test coverage for SlaveSynchronize

[TanXiang7o]

fix #8421
before:

after:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.48%. Comparing base (bd61774) to head (e24901f).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #8422      +/-   ##
=============================================
+ Coverage      45.36%   45.48%   +0.12%     
- Complexity     10987    11003      +16     
=============================================
  Files           1274     1274              
  Lines          88970    88970              
  Branches       11434    11434              
=============================================
+ Hits           40359    40470     +111     
+ Misses         43581    43446     -135     
- Partials        5030     5054      +24     

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[ShannonDing]

link #8262