fix(infrastructure): point all tests to es6 files for accurate test coverage

[moog16]

Test coverage was inaccurate (and very low), since the coverage framework was looking at the package.json main files.

This PR changes the test files to only import from ES6 files. It also performs an npm run clean before running the unit tests. This will force istanbul to use the index.js ES6 files instead.

Before and after pics attached:

[codecov-io]

Codecov Report

Merging #198 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #198   +/-   ##
=======================================
  Coverage   98.78%   98.78%           
=======================================
  Files          18       18           
  Lines         661      661           
  Branches       62       62           
=======================================
  Hits          653      653           
  Misses          8        8

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