Use pytest fixtures to serve the test data

[cmalinmayor]

Closes #106

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.47%. Comparing base (1667678) to head (20d6f95).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
- Coverage   93.74%   93.47%   -0.27%     
==========================================
  Files          33       32       -1     
  Lines         815      782      -33     
==========================================
- Hits          764      731      -33     
  Misses         51       51              

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[cmalinmayor]

The coverage percent goes down very slightly because the test data was considered "tested" code previously, and now it is not. This is fine.