experimental/long-running tests

[fredbi]

This PR investigates why some older detailed tests are now failing.
These (long running) tests are not really maintained any longer and don't run on CI.
However, this bugs me to find them failing... Just to be clear, I have no plan to revive this super-strict test suite that impedes maintainability.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ff196e5) 92.40% compared to head (e2ce530) 94.19%.

❗ Current head e2ce530 differs from pull request most recent head 5545d81. Consider uploading reports for the commit 5545d81 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #163      +/-   ##
==========================================
+ Coverage   92.40%   94.19%   +1.79%     
==========================================
  Files          22       22              
  Lines        2987     2978       -9     
==========================================
+ Hits         2760     2805      +45     
+ Misses        182      149      -33     
+ Partials       45       24      -21     

Flag	Coverage Δ
oldstable	94.12% <ø> (+1.79%)	⬆️
stable	94.19% <ø> (+1.79%)	⬆️

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