test lint() in test-lint

[MichaelChirico]

Companion to #2145.

[MichaelChirico]

File names must not differ just by case to be usable on all R platforms.

I see... that's somewhat annoying.

[codecov-commenter]

Codecov Report

Merging #2146 (25c2866) into main (a93d597) will not change coverage.
The diff coverage is n/a.

❗ Current head 25c2866 differs from pull request most recent head 1d22783. Consider uploading reports for the commit 1d22783 to get more accurate results

@@           Coverage Diff           @@
##             main    #2146   +/-   ##
=======================================
  Coverage   99.64%   99.64%           
=======================================
  Files         112      112           
  Lines        5110     5110           
=======================================
  Hits         5092     5092           
  Misses         18       18