Add test for utils module

[shunichironomura]

• Remove environment variables reset in tests
• Add unit tests for utils in capsula module

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (effbfa0) 48.35% compared to head (c41cac5) 52.60%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #184      +/-   ##
==========================================
+ Coverage   48.35%   52.60%   +4.24%     
==========================================
  Files          27       27              
  Lines         730      730              
==========================================
+ Hits          353      384      +31     
+ Misses        377      346      -31     

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