Add tests targeted at un-covered lines of code

[joshlf]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.64499% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.36%. Comparing base (5226dee) to head (66f9c81).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/error.rs	96.26%	4 Missing ⚠️
src/layout.rs	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2833      +/-   ##
==========================================
+ Coverage   88.14%   92.36%   +4.22%     
==========================================
  Files          20       20              
  Lines        5450     5819     +369     
==========================================
+ Hits         4804     5375     +571     
+ Misses        646      444     -202     

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