Add spec unittest

[oruebel]

Motivation

This PR is to improve unit test coverage for the spec module. Most tests were generated using Cline.

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.34%. Comparing base (b8a1a26) to head (8ddea90).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1243      +/-   ##
==========================================
+ Coverage   90.87%   91.34%   +0.47%     
==========================================
  Files          42       42              
  Lines        9537     9537              
  Branches     1926     1926              
==========================================
+ Hits         8667     8712      +45     
+ Misses        576      542      -34     
+ Partials      294      283      -11     

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