Add unit test for atomic sorting feature
Add unit test for atomic sorting feature

aequitas/isort,levic/isort,jmullan/isort,pahko/isort,jamesbroadhead/isort,tomviner/isort,graingert/isort,leepa/isort,leepa/isort,pahko/isort,AbsoluteMSTR/isort,PyCQA/isort,tomviner/isort,adamchainz/isort,graingert/isort,wimglenn/isort,AbsoluteMSTR/isort,jmullan/isort,adamchainz/isort,gforcada/isort,levic/isort,jamesbroadhead/isort,wimglenn/isort,gforcada/isort,aequitas/isort,PyCQA/isort