test: accommodate slight triangle grid variations

[wpbonelli]

Triangle can give slightly different results depending on platform and compiler

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.5%. Comparing base (556c088) to head (d661242).
⚠️ Report is 160 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2757      +/-   ##
===========================================
+ Coverage     55.5%    72.5%   +17.0%     
===========================================
  Files          644      677      +33     
  Lines       124135   132626    +8491     
===========================================
+ Hits         68947    96228   +27281     
+ Misses       55188    36398   -18790     

see 580 files with indirect coverage changes

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