Restructuring unit tests with their own sub-dirs

[nariman87]

Context for changes

• Improvements:
  • Unit tests have been re-grouped in individual sub-dirs inside tests/ based on error correction and software layers. This helps manage and target each test unit.
  • build_tests.yaml workflow now supports executing unit tests in parallel using pytest-xdist package. GitHub runners have at least 2 processors, which helps speed up the pytest blocks by ~1.5 times in practice.

Example usage and tests

• Not Applicable

Performance results justifying changes

• Not Applicable

Workflow actions and tests

See the updated .github/workflows/build_tests.yaml.

Expected benefits and drawbacks

Expected benefits:

• unit tests now have their own sub-dirs based on error correction and software layers and are faster to run thanks to xdist parallelization.

Related Github issues

• Not Applicable

Checklist and integration statements

• My Python and C++ codes follow this project's coding and commenting styles as indicated by existing files. Precisely, the changes conform to given black, docformatter and pylint configurations.
• I have performed a self-review of these changes, checked my code (including for codefactor compliance), and corrected misspellings to the best of my capacity. I have synced this branch with others as required.
• I have added context for corresponding changes in documentation and README.md as needed.
• I have added new workflow CI tests for corresponding changes, ensuring codecoverage is 95% or better, and these pass locally for me.
• I have updated CHANGELOG.md following the template. I recognize that the developers may revisit CHANGELOG.md and the versioning, and create a Special Release including my changes.

[codecov]

Codecov Report

Merging #70 (0383e7e) into main (1363792) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #70   +/-   ##
=======================================
  Coverage   96.28%   96.29%           
=======================================
  Files          36       36           
  Lines        2233     2238    +5     
=======================================
+ Hits         2150     2155    +5     
  Misses         83       83           

Impacted Files	Coverage Δ
flamingpy/codes/surface_code.py	97.31% <ø> (ø)
flamingpy/decoders/decoder.py	98.42% <ø> (ø)
flamingpy/decoders/unionfind/algos.py	99.27% <ø> (ø)
flamingpy/decoders/unionfind/uf_classes.py	99.08% <ø> (ø)
flamingpy/examples/decoding.py	100.00% <ø> (ø)
flamingpy/utils/viz.py	90.22% <ø> (ø)
flamingpy/_version.py	100.00% <100.00%> (ø)
flamingpy/cv/gkp.py	92.85% <100.00%> (+0.12%)	⬆️
flamingpy/cv/macro_reduce.py	95.68% <100.00%> (ø)
flamingpy/cv/ops.py	91.66% <100.00%> (+0.09%)	⬆️
... and 1 more

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[sduquemesa]

Thanks for this @nariman87, it does make the testing suite much more organized and focused. Overall it looks great! I have left some comments and question, in the meantime perhaps other code-owners can review the PR as well.

[sduquemesa]

Thanks @nariman87 for addressing all the comments! ✨ Let's see what are @ilan-tz's opinions on the quick-install/install issue before merging.

[ilan-tz]

Great - an important PR with several nice improvements. Just have a few small questions.

EDIT: Saw previous discussion! All good.