refactor test & add codecov

[cglotr]

• Refactor test to generate coverage reports
• Add workflow for codecov

[codecov-commenter]

Codecov Report

:exclamation: No coverage uploaded for pull request base (main@cff1bb6). Click here to learn what that means. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #19   +/-   ##
=======================================
  Coverage        ?   97.90%           
=======================================
  Files           ?        6           
  Lines           ?      143           
  Branches        ?        0           
=======================================
  Hits            ?      140           
  Misses          ?        3           
  Partials        ?        0           

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[cglotr]

@imranariffin removed tokens & fix readme badge paths. can help to merge this?