Modify batch processor test use flush instead of sleeptime

[mohammadVatandoost]

For #2670

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.3%. Comparing base (81fea07) to head (3450b50).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2675     +/-   ##
=======================================
- Coverage   79.3%   79.3%   -0.1%     
=======================================
  Files        123     123             
  Lines      22660   22654      -6     
=======================================
- Hits       17977   17971      -6     
  Misses      4683    4683             

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