Add more unit tests (part 2)

[slifty]

This PR adds unit tests for the remaining utils.

Related to #33

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 6.10%. Comparing base (3a97507) to head (c13a48b).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##            main    #770      +/-   ##
========================================
+ Coverage   3.64%   6.10%   +2.46%     
========================================
  Files         33      33              
  Lines       1015    1015              
  Branches     158     158              
========================================
+ Hits          37      62      +25     
+ Misses       978     953      -25     

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[liam-lloyd]

After synchronous discussion of how we want to consistently structure our tests @slifty and I concluded the its here should be tests