Add unit tests for line counter

[mohsen1]

I'm curious if not using require('os').EOL for splitting lines in lineCounter is problematic or not. Since I don't have a Windows machine I'm testing this in your CI! :D

[codecov-io]

Codecov Report

Merging #1444 into master will increase coverage by 3.5%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #1444     +/-   ##
=========================================
+ Coverage      87%   90.51%   +3.5%     
=========================================
  Files          80       80             
  Lines        4286     6133   +1847     
=========================================
+ Hits         3729     5551   +1822     
- Misses        557      582     +25

Impacted Files	Coverage Δ
src/Logger.js	83.06% <0%> (-13.78%)	⬇️
src/packagers/CSSPackager.js	87.87% <0%> (-12.13%)	⬇️
src/assets/PugAsset.js	88.57% <0%> (-11.43%)	⬇️
src/assets/JSONAsset.js	84.61% <0%> (-8.72%)	⬇️
src/utils/getRootDir.js	86.11% <0%> (-8.34%)	⬇️
src/worker.js	92.1% <0%> (-7.9%)	⬇️
src/HMRServer.js	85% <0%> (-6.67%)	⬇️
src/Bundle.js	93.05% <0%> (-6.2%)	⬇️
src/packagers/JSPackager.js	82.74% <0%> (-5.83%)	⬇️
src/Pipeline.js	93.06% <0%> (-4.89%)	⬇️
... and 47 more

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[DeMoorJasper]

Wait what is codecov just not working properly?
This should increase test coverage right?

[mohsen1]

my bad. I left the .only there :(

Suggestion: Your lint rules should be a bit stricter as this project grows.