test: add tests for padding util functions

[lholmquist]

• This adds tests for both the rightPad and leftPad utility function.

While going through #71 and #70 I noticed that this class was missing a couple test cases.

This should bring the test coverage up to 100% for those particular functions

[codecov]

Codecov Report

Merging #75 into master will increase coverage by 1.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #75      +/-   ##
==========================================
+ Coverage   57.14%   58.25%   +1.11%     
==========================================
  Files          18       18              
  Lines         448      448              
==========================================
+ Hits          256      261       +5     
+ Misses        192      187       -5

Impacted Files	Coverage Δ
lib/utils.js	74.19% <0%> (+16.12%)	⬆️

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