ProductsSorter with property testing with 1 variant
Add nil values, apply to_i, spec is failing
Add shrinking
Fix bug on nil values, fix tests
2 variants per product, bug shows up
Bug fix: Partition when any variant != 0
Add 'classical' spec
Introduce regression in sort, prop testing finds it
Revert "Introduce regression in sort, prop testing finds it"

This reverts commit a8a689a18bfce6089c37d8795cd610031c54da51.
Introduce another bug, found by property testing