test(cli): improve test coverage

[kt3k]

This PR adds test cases of parseArgs. This also removes a dead line.

The test coverage of parse_args.ts improves from 97.65% to 98.99%

part of #3713

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.17%. Comparing base (3a93085) to head (8b4caa0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5046   +/-   ##
=======================================
  Coverage   92.17%   92.17%           
=======================================
  Files         487      487           
  Lines       38797    38796    -1     
  Branches     5433     5440    +7     
=======================================
+ Hits        35761    35762    +1     
+ Misses       2981     2979    -2     
  Partials       55       55           

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