yarn-operator: add uts

[zwzhang0107]

Ⅰ. Describe what this PR does

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c8a0705) 56.65% compared to head (f255d51) 73.37%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #63       +/-   ##
===========================================
+ Coverage   56.65%   73.37%   +16.71%     
===========================================
  Files           2        2               
  Lines         353      353               
===========================================
+ Hits          200      259       +59     
+ Misses        135       77       -58     
+ Partials       18       17        -1     

Flag	Coverage Δ
unittests	73.37% <100.00%> (+16.71%)	⬆️

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