Enhance the test coverage

[jrycw]

This PR tries to enhance our test coverage.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.61%. Comparing base (7eae1f2) to head (bc868dd). Report is 37 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
+ Coverage   83.51%   85.61%   +2.09%     
==========================================
  Files          41       41              
  Lines        4308     4317       +9     
==========================================
+ Hits         3598     3696      +98     
+ Misses        710      621      -89     

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[jrycw]

Thanks for sharing this tip with me. Actually, there are times when I get confused about why the formatter doesn't perform as I expected, but now I understand the reason.

[machow]

Thanks again for this---this kind of stuff is so helpful!