This ticket is part of an aspirational goal for the isort project to achieve zero regressions through the remaining life of the 5.0.0 release, without slowing down the release velocity.

Currently, as mentioned by @karrtikr there have been an unfortunate number of regressions in the 5.x series involving the usage of streaming from stdin. This ticket represents the work to expand the automated test suite to ensure every CLI flag is tested against this mode of usage to avoid further regressions.