Add tests comparing integrals vs gamma function decompositions

[anastasia-popova]

Purpose

To-do

Content

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• [ ] I have read and checked the items on the review checklist.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 98.03922% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 96.87%. Comparing base (c71fa8b) to head (6bee931). Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
+ Coverage   96.83%   96.87%   +0.04%     
==========================================
  Files          35       36       +1     
  Lines        1357     1407      +50     
==========================================
+ Hits         1314     1363      +49     
- Misses         43       44       +1     

Components	Coverage Δ
src	98.85% <98.03%> (-0.04%)	:arrow_down:
ext	69.79% <ø> (ø)