data-plumbing-for-corporations tends to be able to be done in a way that’s easily testable, but also most people get paid to bolt on new shit onto old shit and spending time on “done” code is discouraged so once they fall behind on writing tests while developing the new shit those tests will never be written.

and bad developers that won’t write tests no matter what actually do exist.

i’ve only read about rust, but is there a way to influence those automatic implementations?

equality for example could be that somethings literally point to the same thing in memory, or it could be that two structs have only values that are equal to each other