Add tests for internal utilities

[sashabaranov]

Summary

• add tests covering failer, helpers, and server utilities in internal/test
• add basic success path tests for the checks helpers

Testing

• go test ./...

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https://chatgpt.com/codex/tasks/task_e_68713f210bdc832581fd744726d7b87e

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (e6c1d3e) to head (3b9c5f2).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1044   +/-   ##
=======================================
  Coverage   99.59%   99.59%           
=======================================
  Files          34       34           
  Lines        2205     2205           
=======================================
  Hits         2196     2196           
  Misses          6        6           
  Partials        3        3           

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