Improve code coverage

[WilliamBergamin]

Summary

This PR aims to improve the accuracy of code coverage by

• Excluding the integration tests
• Adding unit tests to explicitly include all the end user code in the coverage.
• Adding unit tests to explicitly include and generation script in the coverage.

I also took the liberty to add a few unit tests to improve code coverage

testing

1. pull this branch
2. run deno task test to execute all tests
3. run deno task coverage to execute the code coverage

Special notes

Should the generation scripts be included in our code coverage? (this code is not directly used by the end user)

Requirements

• [x] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.
• [x] I've ran deno task test after making the changes.

[codecov[bot]]

Codecov Report

Merging #213 (1a0bbed) into main (c8b372f) will decrease coverage by 1.27%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #213      +/-   ##
==========================================
- Coverage   99.24%   97.97%   -1.27%     
==========================================
  Files          56       58       +2     
  Lines        2128     2177      +49     
  Branches      135      137       +2     
==========================================
+ Hits         2112     2133      +21     
- Misses         15       42      +27     
- Partials        1        2       +1     

Files	Coverage Δ
src/datastore/mod.ts	100.00% <100.00%> (+3.57%)	:arrow_up:

... and 4 files with indirect coverage changes

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