I disagree, dependencies can change causing types to change which requires you to alter hundreds of lines across multiple repos. Each new line or character is

I disagree, dependencies can change causing types to change which requires you to alter hundreds of lines across multiple repos. Each new line or character is a line to maintain, there is a cost associated with that. Tests have costs but are extremely valuable, they are a no brainer to me, types are way less obvious. I have spent a lot of time maintaining python types. I have no idea how many bugs it has prevented. I am not sure it is a large number. I know there have been bugs in types, bugs in mypy and dependency changes which created work which only existed because types were in place. There have definitely been days worth of types maintain. There are the extra type imports, extra time to run tests and integration tests etc. It is not as straightforward as you might initially assume.