chore: increased test coverage for handler.rs

[lmammino]

Added more tests for the handler

[codecov]

Codecov Report

Attention: Patch coverage is 97.53521% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 94.36%. Comparing base (4670d45) to head (d149c59).

Files	Patch %	Lines
src/handler.rs	97.53%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #16      +/-   ##
==========================================
+ Coverage   90.89%   94.36%   +3.46%     
==========================================
  Files           9        9              
  Lines         923     1207     +284     
==========================================
+ Hits          839     1139     +300     
+ Misses         84       68      -16     

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