Add Bryan/Fritsch warm bubble test case

[benegee]

Just the libelixir.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.27%. Comparing base (1542888) to head (768fdd4).

❗ Current head 768fdd4 differs from pull request most recent head fac2a42. Consider uploading reports for the commit fac2a42 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #176   +/-   ##
=======================================
  Coverage   80.27%   80.27%           
=======================================
  Files          19       19           
  Lines         715      715           
  Branches       50       50           
=======================================
  Hits          574      574           
  Misses        137      137           
  Partials        4        4           

Flag	Coverage Δ
unittests	80.27% <ø> (ø)

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