Add missing LLOC checks

[marco-ballario]

This PR adds some missing checks on the LLOC metric in some unit tests for the LOC metrics. Thanks in advance for the review.

[codecov-commenter]

Codecov Report

Merging #739 (210bf85) into master (f9c1454) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #739   +/-   ##
=======================================
  Coverage   37.95%   37.95%           
=======================================
  Files          51       51           
  Lines        6549     6549           
  Branches      963      963           
=======================================
  Hits         2486     2486           
  Misses       3403     3403           
  Partials      660      660           

Impacted Files	Coverage Δ
src/metrics/loc.rs	77.37% <ø> (ø)

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