When we write custom management commands, it’s easy to write integration tests for them with call_command(). This allows us to invoke the management command as it runs under manage.py, and retrieve the return code, standard output, and standard error. It’s great, but has some overhead, making our tests slower than necessary. If we have logic separated out of the command’s handle() method, it improves both readability and testability, as we can unit test it separately.| adamj.eu
Django requires every change to model fields and meta classes to be reflected in database migrations. This applies even to things that don’t typically affect the database, such as Field.choices. When iterating on code, it’s easy to make a model change and forget to update the migrations accordingly. If you don’t have any protection, you might even deploy code that crashes due to out-of-date migrations!| adamj.eu